when i was first lerning 270s off, i found trying to drop my toes down or up way to difficult, so i just tryed winding up a tiny bit with one arm, and right at the end of the rail i spin my arm around, but this wass for front side 270s. when i first started learning backside 270s i tryed them on a box (a really short one), and i would get on and have my body turn slowly (by the time i was at the end of the box i was looking at the beginning of the box) but my skis still stay sideways and i would just pop off and my skis would turn around. This method worked just to get the fealing of 270ing off blind side. but once you do it on a rail, just i find try to turn your body around and your skis will follow.  I hope that helps.