Shoot Where You Look
This book can be downloaded and read in Apple Books on your Mac or iOS device.
All the instruction money can buy won't make you a better shotgunner unless, and until, these BASICS are mastered:
Consistent gun mount. Mount to cheek-then to shoulder. Focus on part of a target-not on the gun. If a target is moving the gun must move with the target AS the trigger is pulled.
I have used this program and so have my children. There are all excellent shooters now. Lot of people are amazed when they shoot a dime or a penny out of the air with there bb guns. If you want to learn to shoot shotgun this is the only program you need.