uh, mike, baby-steps, dude.
justin's right. do a regular backroll. 3 quarters of the way around, let go of your lead hand and take the handle on your buttcheek. don't let go too early as it will sort of stall your rotation, and you might end up short. that'll definitely hurt.
the best thing to do is to get your hs 180s down. try initiating the rotation at the peak, if not the way down of your jump. that will teach you to ride off landing switch late.