Luffy figured out he could beat Enels mantra by creating random bouncing attacks he could not predict.
He also used blood/water to beat cocodrile.
he used a mirror on foxy slowbeams.
He binded kuros super-fast body, and took adventage of his rubber neck to head-butt him.
He figured out he could do inhuman doppings to his rubber body like blood acceleration and bone inflation.
he used mr. 3 Wax restriction attacks to his own benefit.