Ball and Dummy drills are good to tell you that you flinch but not the way to stop doing it.
Once you know you flinch now you have to take focus away from "noise, sound, flash, recoil" and direct that attention to the positive. Aiming correctly and pulling the trigger correctly; controlling the lift, bringing the sights back to target, then "sending" the sights back up as you shoot again.
This is mental. Let recoil flash noise happen; control it - you make it happen; focus on the sights, your trigger, your grip...