There's as many methods as users, but mine likes to see you walk it up from the groin to center mass for speed if you know what I mean. I have a friend that has a decade old set up; Streamlight M6 laser/light combo. It's set up for using your thumb vs. foregrip. Very reliable. What ever your friend gets make sure he trains often.With a laser on a pistol you will train yourself without realizing to wait for the dot. After all the immediate stress you talk about what happens if you don't see the dot? This is why practice practice practice with point shooting from a low ready position or from a closed holster if the range allows it will train you to raise gun look forward and fire center of mass. Do it enough it will become second nature. I practice with a .22 pistol and coke can if I can. No sights lok at it and plink it all over back and forth. You will soon learn point shooting. Me personally, I wish they made pistols flat top no sights.
I've been told the M4 is acceptable for CQB / home defense. The 14.5" barrel doesn't allow a round thrown short distances to pick up full velocity. I prefer my Glocks for my own reasons, most will tell you a shotgun. Just be proficient with your tools.