I've been fiddling with my bar warmups a lot lately, at the moment, my Lv.3 warmup looks something like this: (probably won't keep it like this for long, but it's been working ok)
1m straight body hang on high bar
1m exaggerated hollow body hang on high bar
everyone gets into a cast position on floor, and I move around and shape all of them until they look nice
10 "Negative casts", just kick to handstand on floor, and lower to cast position slow enough that it doesn't make a "bang" (I tell them they can count the ones that would be allowed in a library lol)
10 casts on a low or high bar
10 undergrip casts on a low or high bar
5 front hip circles, 5 mill circles, 5 back hip circles.
Whoever finishes their stuff first is allowed to start working kips with me if they're ready. when everyone is done with their warmup, I explain the stations we're doing (each is focused on specific problems that we have, like piking in underswings, bending elbows in casts, or 1 arm support stuff for the cutback)
we then do ~2 minute rotations on 4-5 stations until everyone has been around once, then everyone comes to my bar and we see who can make the best kip (or their first kip) with the extra time we have left. we have 12 girls in this group.
Lv.4 is similar.. just more concentrated on kipping