I knit Continental, but don't use my thumb for purling. I use my middle finger (counting my thumb as a finger). I do it exactly like Amy (the gal who does the videos on this site). I know there are people who use their thumbs. I just tried it and it seems harder to me, and I have trouble with my left thumb from just holding the needle, so I don't think it would like doing this.
But I know lots of things that don't work for me work for others. I don't know of a specific video I can suggest, but if I was looking for this sort of thing, I would try You-tube. You can search their site and they have a lot of knitting videos.