Right hand strumming ala School Days
 

Really struggling to get this down, it's most famously done in School Days by Stanley Clarke. But also in the beginning of 'U Can't Hold No Groove' by Victor Wooten.

I can get a sound out, but not a nice consistent one like how it's meant to be. The motion seems to be from the arm, wrist and fingers all at once. Very weird.

Any tips on that?

Example: http://www.youtube.com/watch?v=gl-CxMiW-1Y