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For rotator cuff see about getting some rings and doing pull ups on them, allowing joints to move as they desire in a pull up should make it less painful.
and yes the long and short of it is "do more pull ups" with a side dish of "get stronger at pulling in general".
If you can do 4 or 5 then yeah best method will be just doing more pull ups probably. You could try greasing the groove - doing extremely submaximal sets (like, 1 pull up) many times a day. Like, 10-20 times, but spread throughout the day.
I found success in pyramid sets. Do a rep, rest for a short period, do 2 reps, rest, etc, until you fail a set, and then do back down. e.g. 1-2-3-4-5-6(fail@5)-5-4-3-2-1, and for the sets going back down add in negatives when you can't complete a rep.
If you want to really prio them you could look at the russian fighter pull up program https://www.strongfirst.com/the-fighter-pullup-program-revisited/
I know the answer to this but the only way to get better at pull-ups is pull-ups right?
They make me feel fat and weak.