I have old and new sets.
I mostly play my Mizuno MP-67's - about 10 years old.
My Miura MC102's - about 6 years old.
My Pinc ISI BeNi's - about 20+ years old... sometimes my Eye 2 BeCu's as well and they are 25+ years old!
Flighting, as @iacas pointed out, is another very good technique to take distance off of a full swing distance.
I use the shorter backswing/shorter follow through method. Because I find it's simpler... I struggle with flighting. If I want to hit a lower shot, I take more club with less swing.
I get what you mean by decelerating though with 3/4 swings. Sometimes it happens to me, and I bottom out too soon, and there you go chunky monkey. My swing thought for those of you who use the shorter swing method (primarily with wedges), is keep your downswing the same tempo as if you were hitting a full shot.
That's just my thought, remember I'm not a pro, and I surely don't claim to be.
It's his business what he does or doens't do. You can encourage his interest, or just stay out of it.
I'd absolutely decline the request to teach him and just tell him if he's going to do this, he should get lessons.
as for the other thing, he wants to bond with you on this.....I'd just say you like playing 'good' golf with players of similar skills. So if he wants this hobby to turn into a 'bro' thing, he has to take lessons and get nice gear and be good enough to enjoy the same course difficulty you do. And you're happy to wait for that, but shouldn't plan to play a lot with you until then.
It's not your business what he does
it is your business if he wants to do this to be buds with (but only that aspect)
It's a HARD transition to go from work focus to retirement - this might be a great thing for this guy