Having tracked down a photo of the tool, I would think it works rather similarly to the method used in this video: . Admittedly, Kelly Alwood uses a Bic pen in that video but I would assume the basic technique is essentially the same given the appearance of the tool in the images I found.
Interesting, thanks for the video. I've seen Bic pen barrels used for an impressioning attack on an Ace style lock (the famous bike lock 'hack') but the motion he is using here is a little weird. I guess I'll have to get some Darby style handcuffs and see how they work...
