At the time of the shot my middle finger is on the 'W' key, my left ring finger is on the 'Q' key. Immediately after you take the shot (you hear the shot or you depress the fire button) tap the Q key twice. To practice I'd say just stand still and take shots practicing the two-tap quickswitching and when you can do it reliably for 4 shots (don't do it on the 5th, you'll waste time reloading!) then start moving around and practice left strafing while quickswitching which is obviously harder because you have to move the ring finger off the strafe key to hit the key above it.
I don't know about the rest of you guys who use it but the worst part about quickswitching is you tend to switch before the shot is even sent in your haste to be fast, oh well :confused1: