Shot Follow-Through Advice?

I've seen many resources on precision shooting stress the importance of follow through and making sure that you're on target before and after the shot. This happens very rarely for me, but my groups are significantly better when it does. Typically, after two or three shots my rear bag (Armageddon pint-size game changer) will lose it's structure and I have to keep squeezing it harder to try and maintain natural point of aim. Eventually my grip fatigues and I find myself aiming with the rifle grip instead of the bag. Any tips on improving follow through?