Well, goddamn. After years of playing and re-playing, I finally realized that to wall-jump consistently, all you had to do was press the (opposite) direction you're jumping to ever so slightly before pressing jump--my problem was that I would do this by "accident", when in reality I was always trying to press them simultaneously. It's a particular timing, but once its down, you are set. I was always a mediocre wall-jumper, using it only as needed (which is what, the one spot where the little alien dude teaches you?). But now I can finally try and navigate at will to see what I can do ahead of time/out of order, plus now I can mess with some of the harder hacks that make you wall-jump. The game just keeps giving.
Oh, as for hacks, I've been playing one called Super Zero Mission. I tried it because apparently its a reasonable sort of difficult that doesn't rely on the higher-level techniques to get around. It's really been awesome so far.