let me clarify... if doing a jump or whatnot, i am more comfortable spinning left than right... but to get on a rail i spin right, and grind with right foot forward
when you pop on look at the end of the rail and stop yourself from turning your head and shoulders whcih will make you slide off grip the rail to set for spins off
when you wanna do a front switchup you really dig that front edge into the rail, kinda pushing that front heel down into the ground. be patient with it though make sure you get on and lock on full 90 degrees before gripping the rail like that or else you wont be able to change your momentum.
get a long box to pretzel on and if its like 2 feet wide(270s can be scary onto rails) try to get your toes on the edge of the box to scissor and spin out. At least thats how I learned them.
i spin right onto rails but spin left in air, i think your trying to say that you slide left foot forward, or you would always be doing 270 on to rails, unless thats what your asking about