I dont believe in dry firing to excess. Not with out snap caps.
The coin idea is a good one but what I find works best is to use a revolver and have some one load it for you so that you cant see and leave one or two empty chambers. You can do it your self but you have to spin the cylinder and close it with out looking.
When you add the recoil and the noise it makes a difference in the way you handle the gun.
It will also allow you to see what your doing IF you pay attention to those times when the gun does not go off. Like pushing the gun forward, pulling right or left or just poor trigger pull.