When you say practice, how much time are you talking about?
Say, about three times a week for about an hour each session for example?
The best practice is just a few arrows ever 2 or 3 days. Most start out and practice too much, once you start shaking you’ve went too far. I usually shoot no more than three arrows then lay the bow down and go to the target just taking my time. I’ve seen too many that want to shoot every arrow they have and by the fourth or fifth shot they’re string them all over the place. Start at about 10 yards and slowly work back. With my recurves and longbows I’m good to about 25 yards and group nicely at 40 with my compounds. Started shooting a bow when I was 7 I’ll be 63 this November and have yet to miss a season. While I really enjoy the speed and accuracy of my compounds the simplicity of the stick and string are hard to beat. Tell him to start light and slow and it won’t take long for that shoulder to get back in shape. I will give you one word of caution traditional archery is quite addicting. Good luck to you both.
One hour of slinging arrows is way too long, I shoot several times a week and I rarely go over about 15 minutes, much longer than that and muscles get tired and shakey and you start lossing your concentration. When I shot competition we would shoot all day and for me to keep up I had to practice extended shooting durations to keep up. I no longer shoot competition and strictly hunt and with that it’s the first shot that counts you rarely get a second. I would suggest he start one shot and retrive his arrow giving him and the shoulder plent of time to rest. I use a calf skin glove but there are severl different tabs that work just as well and are less binding. I shoot strictly aluminum arrows with 4 to 5 inch vanes in my longbows and recurves and carbon fiber with the shorter Blazer vanes in my compounds. Carbon fiber and recurves are longbows don’t seem to shoot well together for me.