I have found a method to build strength but not sure if it increases size. It requires zero equipment, no walls, doors, no pushups, dips, pullups.
I can't find it anywhere online, but basically, I just imagine I have a set of cables and visualize exercises with the cables, for example, I might do a chest press, so I imagine holding the cables, and with full exertion with a slow and steady pace, push forward, You get about 8-10 reps, before you are spent. Instead of exerting a force against a weight, you are using your full capacity throughout the whole exercise.
I've seen a Circus performer doing the exercises, and he wasn't huge, but extremely strong.