After a normal wrists catch, swing into the apron and lift both legs up to the catcher's right shoulder. The catcher takes both legs and lets go of the right hand. Push your hips through into a straight position. Reach for the bar with your right hand. At the peak, let go and take the flybar with both hands. Of course, if you prefer, you can do everything on the other side...
You can find out more about this trick in my books: