Do not do kipping pull-ups or cross your ankles when you do a pull-up. You'll risk severe injuries.
If you want to maximize your gains then do a regular pull-up. Start off with your hands a little bit further from your shoulders and do a dead hang. You want to do a dead hang as it will help...
@Vahneris You don't need to make a character train like ohma or saitama. The character is supposed to be believable. If the whole manhwa isn't suppose to be like that then I wouldn't complain. The manhwa doesn't imply its all suppose to be a joke that hes winning.
Unless he joins a mma gym hes not going to become a relatable character because no one can beat a pro athlete just by watching a couple of videos on the internet. It's just going to be a stroke of luck every time he fights, its gonna get stale.