There's lot to consider. He can start with the POI/POA links in the first one,read that, make changes as necessary or take the time to do things right. The POI/POA stuff is at the bottom 6715.0 link.
Researching in depth is a part of this.
Since we are not present physically to see how he shoots and the techniques it's hard to know what needs changing if anything at all. Too many variables to check.
He asked for a lot within the simple queries he has proposed.
Stance, how the gun is held, thumbs high.thumbs low, bullet and cartridge weights and combos, gripping the gun, finger pressure on the trigger and the grip itself, foolow through on the trigger, and the other too many to mention variables make it hard to give just general simple advice without going into detail.
That's all provided here.
He can shoose to ignore all this, but he's going to have to go through all the stuff to become proficient. That's whether he does this with other competent teachers or by himself.
Take some time and absorb the lessons learned by others and what they have to offer.
I didn't even get started on having a small reference library and the fact that Paladin Press,Police Book Shelf and
www.krause.com are good places to start one with. Just the basic books by been there done that authors.
Mas Ayoob and Chuck Karwan's Gun Digest Book of Combat Handgunnery are one of THE definitive sources,easy to read, and come with pictures depicting what's being described.
Updating the few reference books on shooting every year or so can't hurt either.
So anyone takes the time to check it all out,so much the better.
Unfortunately we can't video conference his shooting at the range. LOL
Me, overload someone. Naw!!! LOL