Want a quick change up for your average pull up?
I’ve found that draping two towels over the pull up bar and using them to perform your pull up activates your forearms much more effectively than the standard form. The bigger the towels you use, the more difficult the pull up will be to perform. Oftentimes, I will simply use the towels that are laying around that are used to wipe off the equipment if I don’t bring my own (seeing this written out actually makes me realize how grimy that is…so you will probably just want to bring your own.)
In terms of reps and sets — look to be able to perform far fewer than using your standard grips. I don’t even attempt to fight for a certain number, I just go to grip failure…but feel free to experiment with your own rep/set combos.