Does your friend have any part of his other arm? If so, he can tuck it under his arm instead of his waist band. This will be much faster and much easier to reload. I imagine it will also be much easier on the finish of the gun if he typically wears a belt. Sticking a gun in your waist band usually leaves a few marks if it hits your belt buckle or metal buttons on jeans.
I applaud your friend for seeking training. It is a bummer that he only has one arm, but at least he is doing what he needs to do to defend himself.
The ATF should be a convenience store instead of a government agency!