Nice ones :)
The thing that annoys me about this hacker / painter stuff is that it really boils down to: do something with passion, and you will discover unknown depths, whatever the field may be. That's pretty much where every comparison stops.
Recipe to learn a new skill:
1) get the book called "the art of XXX", written by someone who has been doing XXX for the last 60 years, and which has good typography (no shit)
2) skip the intro and first chapter, which is almost always "XXX has taught me a new way to see the world, XXX is a way of life, blablabla"
3) do the exercises that seem incredibly futile in the second chapter, and do them over and over and over and over all your career. In music, that's your scales / hitting just one note deliberately / tempo exercises (I studied jazz bass), in drawing its those shading exercises and figure drawing or just hatching that you can see the guy in the mentioned thread doing over and over (cast drawing / painting). That's stuff you still see masters doing after 60 years. They don't do the crazy fancy whizzbang stuff, they practice pretty much what the beginner has to practice on the first day. Also, it's almost always something very physical, not mind-related. My only real comparison in programming would be: "practice typing", but that only helps for the first few months I guess. After that, more like having a routine of learning new things or practicing existing data structures or so.
4) do it and do it and do it and never worry about finding your own voice or not being good enough or being better than someone else or having envy or getting frustrated. Just do it and when you don't feel like it then at least do the boring exercise stuff and then go out and enjoy the sun or something.
that's it. nothing magical to it. no silver bullet. don't buy the expensive guitar, go for the one that keeps in tune and the amp that doesn't distort. go for the ballpoint pen. you will know when the expensive tool is right when you know it's right.