John, there's nothing real fancy to the integrated handgun/combatives stuff. In fact, I find the simplicity of the whole thing ingenious. The gun is in a retention position with the base of the thumb pressed against the outside of the pec with the muzzle angled slightly down and the other hand ready to jam, deflect, elbow, or all of the above. If you view the supporting arm as a battering ram with your body providing the momentum you can see how you can deflect and arrest someone's forward drive. When there's a clear line of fire, start dumping rounds into them. As soon as you can, head to their flank and start moving the pistol out into a more extended position. If they have friends, you'll have to repeat the process.
Consider also that you might dump a full magazine into someone and they keep coming. If you don't have a default cover/retention position, what will you do if they don't drop right away, even with a bunch of leaking holes in their torso? Also, if the gun gets muzzle averted, you're probably going to start grappling with someone, and that gets very, very ugly. That elbow helps keep them off you.