Swing out from the platform. At the back end, get up into the Whip position. At the frontend, let your legs come forward as if you were moving into a shoulder-dislocation position, give your legs to the catcher and let go of your hands.
Since you need to bring your legs through for the catch, hold the bar in a Regular Grip rather than the Narrow Grip for a normal Whip.
You can find out more about this trick in my books:
Thanks to Alex and Amber for providing a video for this page.