once again, practice :) Maybe you should do some chromatic picking exercise. -1-2-3-4- all over the strings/frets with stringskipping etc. Ripping through some scales would be pretty good too I think.
Picking fast(and descent at the same time) is just moving your pick up and down, simple as that. So you want to move the pick as little as possible to get the fastest speed. The more space there is between each pick movement, the slower you'll be. It's better to use only the tip of your pick (but I guess you already knew that)
I've also seen people who hold their pick between the tip of their thumb and index finger. I find it much easier when I lay the pick on the side (first inch) of my index and give it a some support with my middlefinger when it's hold in position with my thumb. Offcourse you should only do what feels best for you
So:
*As little space between the pickmovements as possible
*Use pick tip
*Give the pick a comfortable position to speed up

Try to relax as much as you can, you don't want to cramp up. Hope I pushed you in the right direction.

Gul

[Edited by Gulder on 04-01-2002 at 05:26 AM]