I can handle max out bench press, or military press till my balls bust, but doing multiple sets of chinups for me is so freaking tough. I can do 10 in a row very slow with good form no problem, then wait 60seconds and try the second set is much harder, can only do like 8, and a third set just rapes me.

any tips ?

Or should I do them in my 5x5 routine I am in the middle of, and add weight to my chinups with a backback ??