I enjoyed this presentation from a Mantis and BJJ practitioner on a possible grappling application of the four move Yang family GST. He mentions a Beijing Shuai Jiao site at the beginning and also a site called Yang Lu Chans Cotton Boxing.
- use left hand to control his opponent's right wrist.
- use right hand to control his opponent's left wrist.
- guide his opponent's left arm under his opponent's own right arm,
- release his right hand, use his right hand to pull down (or lift up) his opponent's right arm.
The whole technique will be perfect. IMO, the less time that you allow your opponent to have free arm, the better chance that your technique will work.