An example of the type of strumming I'm looking at that's fast is the Korn song, Got The Life or especially the System of a Down song Chop Suey, which I realize is probably quite an aspiration to be able to strum that fast.
I've been playing for 15 years, but it's only been in the last year, that I really wanted to try to get faster and try some different techniques.
I haven't had a lesson for ages, but it probably would be a good idea.
For Michael Angelo, I can't quite figure out what he's doing. If he's rotating his wrist ever so slowly, I can't figure it out. It looks to me like it's all from the forearm, but I could be wrong. George Lynch looks like he has his wrist really flat to the board, has his pinkie and ring finger sticking out, and it looks like really minute, mechanical rotations of the wrist. As I remember (and I'll have to look at him again), Yngwie has just his Pinkie anchored, and picks really softly with his wrist angled a bit.
The only way I can pick really quickly is to bend my wrist almost 90 degrees and pick by rotating my forearm, but I have zero control.
Thanks for the advice so far. :)
It does seem though, that if I stick out the knuckle on my thumb when I'm strumming quickly, I go faster. Not quite sure on picking. I've seen people go just as quickly with the knuckle on their thumb locked as they do with it bent a little and the top of the thumb coming around the top of the pick slight. (That seems to make artificial harmonics more difficult though).