I forgot to mention using your pinky, ring finger, or both, as an anchor point on the body of the guitar, which will help prevent arm movement and isolate the stroke to the fingers. You don't want to plant them there, but treat this like you would your thumb on the fretting hand-- just light enough for a foundation, but free enough to move where you need it without holding you there. Good luck. As soon as I can figure out how to get my rig to record onto the computer I will post some fast tremolo picking.