So besides getting the 3 fingers on my right hand consistent and fast, I have been practicing 16th's with my thump, index, middle, then ring. Should I be moving my whole arm down and up (keeping my thumb at the mercy of my arm/hand) or be keeping my hand steady, but move my thump and fingers independently (like one would finger pick a guitar)? How do you do it?

i have a little arm movement. some ppl with hitchhikers thumb dont move at all, its all fingers.

i'll post a video of how i roll... haha pun

You can start out with some arm, but try to minimize it. The arm builds momentum and makes the fingers work less, but if you focus on the fingers, they become stronger and you can economize your movement.

sorry for the quiet and chopy audio, but its the best i can do

http://www.youtube.com/watch?v=FzBfMYunkO0

http://www.youtube.com/watch?v=qig3yw5XqQ0

I would say that it is similar in technique to double thump (not in idea, but in execution) in which your arm moves, but it is mainly in the thumb.