This is interesting article how to train our grips to get better accuracy during handgun shooting:

http://www.dieselcrew.com/how-to-improve-grip-strength-for-shooting

There are different recommendations in this article, but I would like you to pay your special attention to “Hybrid Grip Drill – PVC Banded Hold for Pistol Grip.” It is simplest and cheapest method to train strength of the deltoid muscles, fingers and wrists for accurate handgun shooting. I included this exercise in my regular workout with a stick, and I can say that it works.