Not sure there's one single technique that is a favourite, I've had several different types that really worked. Long and slow works well ... no teeth, no tugging, and no frantic head-bobbing with hand action, just trying to get it over with. One very unusual one I had was a girl who just flicked the side of my helmet with her tongue ... kept doing this for ages, and eventually had the desired result ... very unusual, just the tip of her tongue on one spot for ages, really slow build, but did the trick. Visual element can really hep, as a few guys have pointed out.