Hua Lin,
The double Gwa Choy's follow Dai Ma Chang Choy at the end of 1st Form. You move in and scoop the lead leg with your left and punch to the groin with your right. As you step up lock the left arm over the leg trapping it (locked over your shoulder) as you stand with the right fist positioned just under the leg (the downward fists position). Now retract the left (left Gwa Choy) and fling the leg up and over (right Gwa Choy). That's providing they didn't drop after the groin punch. I haven't tried this on anyone yet. Any volunteers Temple students? :-)
I've wanted to test that application for awhile; had to visualize the movement ever since I learned first form.
Can I try it on you first?
(Not being flirtatious -- it's just that the groin punch sounds wicked painful, I'd like to avoid it myself)
There is a great streak of violence in every human being. If it is not channeled and understood, it will break out in war or in madness. ~Sam Peckinpah