I don't see why he wouldn't be able to convince them to come to a practice session regardless of them having any particular negative feelings about him; they appear to all be willing to train either way and a number of them are working with each other so group efforts aren't an issue to them. He would have secured a place where misfires are acceptable and he would be held accountable, and even if they aren't in it to learn from him, he can offer himself as a literal target to take their emotions out on, and give them snarky feedback as they fail (both correcting their issues, and making them really want to solve those problems to actually hit him an shut him up)