To test eye dominance, the best method is to poke a hole in a piece of paper, hold it straight out in both hands, sight on an object and slowly draw the paper back to the face. The eye it goes to is the dominant eye. It is a disadvantage to shoot with only one eye, especially on teal and driven. Special one eye techniques must be used on these birds. One of the advantages of this method is that the coach and student both see exactly the same lead, not so with swing through.
Proper muzzle starting position is critical in making the correct blend.
Start with the gun butt slightly under the armpit so that the gun must be pushed forward slightly as it is mounted. This is much smoother than starting with the gun butt further forward and simply yanking it straight up with the right hand. Do not always copy the way that your coach shoots. This helps your follow through. It is not necessary to be comfortable when starting the move, just when finishing it.