I did some reading around when I first heard about this.. As the film says, some scientists think it's a response to a possible predator. I think this could be quite stressful for the bird, so go easy! That said, I'll confess I did try it on one of ours, but with only short-lived success!
I can 'hypnotise' the geese though. You hold it still on the ground, with its head under its wing, then repeatedly stroke gently from its neck, all the way down to its back. After about 30 seconds, you feel the goose relax and go to 'sleep'. The trick then is to see if you can back off without it waking up!