Over the years I’ve only done a little bit of bar work. I remember one day back in gymnastics I decided to try out the bar kip. The other people there told me how to do it and in a couple tries I had it down.
This video shows you how its done.
To do the bar kip you need to learn how to use your body. Its not so much a strength move (though a foundation of strength is necessary) but learning how to divert your force when and where needed. You need to be tight at certain parts and explode in others.
Though the end result is being over the bar, this is different than a muscle up, done on the bar. That is more of a pullup or bent arm exercise into the position, even if kipping is used to aid in the movement, while this is straight armed mostly and done completely with body momentum. Of course both are great, just different applications. Actually now that I think about it, you’d probably get benefit in training both of these, in order to improve both to some degree.