Pop using both, for your first few tries anyway. You really can't technically pop with your shoulders, but I get what you're saying powder.ranger. I recommend first trying to slide rails both ways - right and left foot forward. If you slide right foot forward:
FS swap: Try to 'grip' the rail with your right foot, inside edge, at an angle like so " \ ". Right before hitting the FD kink, grip a bit harder and move your shoulder towards the right. At the kink, do a slight pop. Bring'er around and land left foot forward. Keep your left tip up so it doesn't catch on the rail. While you're in the air above the rail, keep your shoulders open, i.e. keep moving them to the right to make sure you get the 180 around.
BS swap: the easy way is to spin a little harder to the left on than you normally do, pop at the kink and continue the spin. The 'true' way is to land normally on the rail, grip the rail with your right foot (forward foot) like so " /" at a slight down ward angle with your right foot, inside edge. Pop at the kink, lift your tips up (can't stress this enough) and land left foot forward. Just like in an FS swap, keep your shoulders open and not locked, but this time they will be facing up hill after setting it.