When I started playing again, I didn't want to be locked into my existing limited models, notes off the page, all major scales, plus the occasional foray into the three minors they teach you in school. If you expand your horizons, however, there are a very large number of possible scales to play with, even if you limit yourself to the ones common used in some musical tradition and ignore the infinities of mathematical possibilities. So I grabbed some of my wife's jazz theory books, typed in the names of some scales, and picked one at random to play from time to time when I was in the mood. I soon got to be able to distinguish a melodic from a jazz minor, minor and major pentatonic, remember the names of all the modes, and so on. I couldn't play them fast or fluently, but I could puzzle through them one at a time, and I felt like I was learning something.
Still, there's always stuff you miss. For instance, it seems reasonable that a minor pentatonic fits inside a minor scale. But there's more. The inimitable Paul Hanson explains something I wouldn't have guessed: in fact, you can fit *three* different pentatonics inside. For a Dorian, you have a minor pentatonic available starting on the 1st, 2nd, and 5th scale tones, all without leaving the scale. (Likewise, you could do major pentatonics starting on 3, 4, or 7, with similar embeddings for any other mode.) In this video, he demonstrates with bass player Craig Harris.