The basic drill for me is make them start in front support on the bar, check they are super tight and not piked, then tell them they have to be like a stick and not change their shape while I push their shoulder backwards (one hand on their upper back and the other on the back side of the thighs)
For the first tries, I'd stop them in the candle position and check again for the position, and the push their legs down while also supporting their shoulders, so they finish back in front support.
Also, I'd do some back drops, starting again in front support and they should drop back a bit until you stop them (you can stand behind them and stop them putting your hands in the upper back). Then do the last part making them lean forward until they're straight and then push their feet so they finish back in the starting position.
Once they can keep their body in a good shape, then I'd make them do the full hip circle from front support, pushing them a little to give them speed.
When mastered, add the cast.
That's for young kids, for older ones, I'd do similarly but with less spotting.
