I've been doing it for 30 years, almost.
Have you been drilling it out of a
chi-sau format? When I wrestled as a youth, I loved the arm drag, but there are some issues applying it in
chi-sau from a Wing Chun perspective:
First, in order to execute a classic arm drag by grabbing your opponent's wrist and behind his elbow, you need to break a Wing Chun rule and
use two arms to control one. Not generally a good idea for a striker. This increases your chance of being hit (unless you've set it up really well) and at the same time prevents you from hitting him.
Secondly, in
chi sau, you are already at a striking range. If you can set up an arm drag, controlling position well enough to be able to grab both wrist and elbow without being hit ...then you can almost certainly just
hit him instead. Seeing as Wing Chun is a striking art, this makes more sense.
Ok, maybe I'm really just saying the same thing twice here ...that a classic, two-handed arm drag is a
grappling move that sets you up to take your opponent's back, take him down, and control his body. Wonderful ...but not particularly helpful in a striking oriented drill like
chi-sau.
Now that said, there are some variations on the arm-drag concept that can be integrated into chi sau.
1. The lap-palm or lap punch entry used in the WT system's
first chi sau-section. Not exactly a classic "arm-drag" since it uses only one hand on each arm, but nevertheless it's a great entry leading to a tight clinch and a sweep/throw finish. Done right, it has a good success rate.
Here's the basic dynamic of this entry demonstrated a long time ago by my old sifu. For the gist of it check out 7:45-8:30:
2. Another way to integrate a more typical wrestler's arm drag would be as a follow up to a simple inward-angled low punch over your opponent's tan-sau. A typical follow-up would be pak-da followed by chain punches. Instead of converting your punch to pak, you could follow up catching your opponent's elbow and going for the arm drag. I've made it work ...but is it worth it?
...Sorry, don't have any video.