I am right handed and I can fire faster with my left. The reason why I think this is the case is from using my left hand to move the arrow keys when playing PC games.
Tap at everything, tap ur pen at work/uni/school etc. Just tap and work up a good beat.
Also play with your trigger settings, the lightest/shortest pull isnt the fastest way for everyone.
Or you could just forget all that and play with ramping.