Hold the gun with just enough force in the right hand to stop it from being able to move freely. So grip it, and then try to push the gun around with your other hand. Then test it in live fire as well, see if you can feel the gun moving in your right hand during recoil. Once you've established what that force is, then do not grip the gun harder than that with the right hand. Instead, most of the grip pressure should come from your support hand.