Allen is dead on. At the Greg's seminar in Orlando he had me doing tall snatches to increase my speed under the bar. Snatch Balances are extraordinarily challenging so use light weights when you start and think about pressing yourself down under the bar. The goal is for the bar not to rise at all from where you are starting. You will have a momentary unloading of the bar but you have to focus on pressing yourself and pulling yourself into the hole.
Here is a complex that Greg programmed that happened to fall on Christmas Day (hence the hat in the video, my son and I were being goofy) Medium Weight Muscle Snatch, Overhead Squat and Snatch Balance. My form isn't perfect but I like this complex alot.
Hope this helps.
What we think, or what we know, or what we believe, is in the end, of little consequence. The only thing of consequence is what we do. -John Ruskin