This might help the flinch. When I take a new shooter to the range. I have them hold the gun down range and tell them to close their eyes. Now have them slowly squeezze the trigger and actually feel the recoil on thier hands and arms, not listening to the noise the gun amkes. I also usually have them wear ear pugs and muffs to eliminate as much harsh noise as possible. After a couple rounds the person usually gets comfortable pulling the trigger.

This does many things. With the eyes closed they do not see the flash of the gun or it moving. They actually feel the recoil with out the brain adding more to it than there is from the movement and noise. Most say "hay that's not so bad". It seesm to help disassociate all the sudden violence and lets the brain realize each action one by one. When the minds knows whats going to happen and it can be controled it's easier to concentrate on the trigger squeeze and the sights without the fear of inpending doom.