its doesnt matter what foot is forward when u slide. for me, i slide right foot forward.
to 270 off (not blindside, where you come out regular), you'll be spinning or sliding unnatty, most of the time. if u slide unnaty, u can spin off naturally. i find it easier to slide normal and spin unnatturally. so what you do is find a rail with a lil drop off the end (bigger the drop= easier to get full rotation off but harder falls). Pop the full 90 onto the rail (well say for me, sliding right foot first). Do the rail normally, with your shoulders parallel to the rail and just your head looking at the end. As you get near the end of the rail like 1 or 2 feet, turn your shoulders so you are looking straight down the hill. Pop off a little bit, and spin. since your shoulders all already turned 90, is basically a 1 out, landing switch.
so for me, i slide the rail right foot first(natural), but spin out clockwise (unnatural)
blindside is when your spinning AND sliding naturally, most of the time. This one is harder cuz u have to spin'up' the hill so its harder to set the roation, and you have to pop more. i used to always only get 180, then biff and smack my head on the ground. so for me, blindside would be slide right foot first and spin clockwise off.