There is a certain "tradition" for some unicorn families When it came to disciplining their children.
 
Colts and fillies naturally get into trouble and require practice to learn how to use even the most basic magic. Because of this, a few unicorn parents came up with way to combine discipline with magic practice a long time ago. The method quickly gained popularity and spread out all throughout Equestria with many unicorns still using it to this day.
 
The method is quite simple, yet effective:
The naughty colt or filly is expected to stand still, bend over an object or lie down on their stomaches and get their tail out of way. They are then tasked with grabbing a spanking implement (usually a brush, paddle or wooden spoon, but it can be anything) using telekinesis and then they have to spank themselves with their given implements.
 
This saves the parents the trouble of manually having to spank their foals and is a good way for said foals to practice their magic and self discipline.
 
Of course, the kids would often try to go easy on themselves, but their parents would supervise the procedure both to make sure that the spanking is as harsh as they want but also safe. They give out commands as needed:
"Hit lower!"
"Hit that spot again!"
"Hit harder!"
"Don't stop, keep going! Faster!"
 
Of course, the colts and fillies know that disobedience means a trip accross their parents knee for a harder and longer spanking so the youngsters are forced to give themselves proper spankings and have to keep going till' their parents descide they had enough.
 
In some cases, extra factors may be given:
The unfortunate colt or filly might have to lift their backsides into the air by the tail using levitation (this requires extra effort) or give their parents detailed reports what they have done wrong and why it was wrong while spanking themselves. Anything can be possible.
 
Parents can also be merciful:
Some fillies and colts might feel guilty for their actions and could end up spanking themselves harder then necessary in which case the parents would intervine:
"You can go a bit lighter."
"Wow, you sure spanked yourself silly. I guess you can stop a bit early."
 
 
 
Early applications:
 
This is how it typically goes for younger kids who would be recieving their first punishments of this nature or for unicorns who have not yet grasped levitation as well as some of the others (no problem, they will learn).
 
The parants in these cases tend to help them concentrate in ways such as holding their tail out of way, picking up the occasionally dropped implement or just giving advice.
 
They would first have the soon-to-be punished colt or filly spend a few minutes lightly tapping every area of there rump before the self spanking to know what to hit and what to avoid. Safety is important, after all.
 
When it is time for their parents to order them to start they usually wouldn't do so immediatly and would require a few theats of harder spankings, some encouragements and a bit of mental preperation to get them going.
 
The first self-spankings tend to go quite slowly as parents would often let their kids take short breaks to gather their courage. They would get more stingy about breaks in later spankings.
 
The colt or filly is usually sobbing and begging parants not to make them swing anymore by the end of it, but tradition also dictates that the final three spanks must be extra hard.
 
The parants help their kids give these last three by magically guiding implement backwards and aiming it for them. They would pull it a lot further back then the colt or filly would.
 
The foal then only has to swing.
"These last ones are to be extra hard so you better make them count!"
"If it's too light you must try again!"
 
The foal really wants to stop by now so they would usually just close their eyes, gather there courage and give themselves a full force swing only to drop implement and start dacing in place. Parants would quickly get them back into position and make them grab paddle again.
 
They would once again help the kids pull paddle back and aim (usually for sit spots).
The colt or filly, just like last time but with even bigger haitation would swing down again and occasionaly repeat of first spanks shenanigens.
 
For the last one, the paddle would be pulled back the farthest of the three and aimed at the meatiest part of the rump.
 
The filly or colt would be sweating, crying and shaking by now and would require a bit of further encouragement
"Just one more. Make it good!"
After this last swing they tend immedietly start rubbing their sore behinds.
 
 
 
Later applications:
 
Some colts or fillies get to a point where they can safely and effectively punish themselves without the need of parantal supervision, which can be very usefull when the parents are doing busy when the foal needs to be disciplined.
 
In these cases a parent would tell them to spank themelves and would either give them implement or make their kids get it themselves.
 
Sometimes parents would even let them choose the implement (this can also happen for foals who still need supervision). A lot of colts and fillies tend to pick something small like a wooden spoon because the small surface area allows them better control over what part of their butt needs to be tortured at a given time.
 
Some prefer larger implements like a large paddle. These cover larger areas per spank and can allow for quicker and more thorough reddening, which some believe can lead to fewer individual spanks needed.
 
Other prefer medium sized implements like hairbrushes or ping pong paddles for a combination of the two.
 
Only a few would ask for tools such as switches and parents are reluctant to give those as it is harder to evaluate a spanking based on lines rather then general reddness.
 
When it comes to the spankings, many foals have different ways of giving it the themselves:
Sometimes, they would focus on one buttcheek until its sufficiently punished and go all out on the other and sometime they would try to distribute the spanks evenly.
 
The parents could also cast a marking spell which would magically mark spots on butt that would need to be hit a certain amount of times. These typically end up being two on both sitspots and two on the middle of each cheek. Often times the naughty foal would get these out of the way first and sometimes end te spanking with them.
 
The parents would always carefully check the bottom after the foal is finished to make sure it is adequately spanked so the children know that their flanks have to be sufficiently reddened.
 
Colts and fillies would sometimes stop and check their bottoms to see where and how much more they would need to spank. Their parents would often be understanding in these cases and even give them small mirrors to check the flanks. This quickly became another tradition for many families: lots of unicorns have their "spanking mirrors" just for self spanking.
 
The young unicorns wouldn't be given a lot of time to check their butts.
"I don't heer the smacking! Do I need to go there?"
 
Cautious parents could also cast a spell to prevent their kids from reaching their butts and these would only be dispelled after the parent inspects colt's or filly's fanny. Sometimes they would suddenly have to leave for some reason or would be too busy leaving poor foal waiting for them with a sore tush they would desperatly want to rub. The worse part in these cases is that reddness of the spanking might start to fade and the unfortunate colt or filly could be forced to get some extra hits in.
 
The inspections after the self-spanking are not always successfull.
"You missed a few spots. Get them covered!"
"I asked for red, not pink! Keep going!"
 
On some occations, the parents might have to intervene if their kid spanks too long or if the hits sound too loud:
"Alright, you had enough! No need to go overboard."
"Stop spanking so hard! We don't want any injuries now, do we?"
 
There is yet another tradition assosiated with self-spanking:
When some kids come of age, their parents might teach them the spell that keeps them from rubbing their butts and the counterspell to it and the now grownup kids would get to keep their most used implement and spanking mirror as an initiation ceremony of sorts. These would usually end up being used by the grandkids leaving mirrors and spanking implements hairlooms for many unicorn families.