Have you ever done misty 4's off of ledges or just on flat ground? Basically taking off sideways and doing a lincoln with a 90 to land switch. If not, I definitely recommend learning them on flat ground or at least off a small drop. It feels almost identical on skis, just comes around slower your first few times. If you just want to go straight for it, really make sure you pop and throw that shoulder down. It helps to set it a little before the end of the rail because your edges will sort of catch the rail and help whip you around faster. Also definitely helps to find a rail with some kick for the first ones.