I kind of don’t have an answer here, but I would say there are two things in what you’re asking: finding tutors for obscure subjects per se does seem a bit more difficult that it should or could be, so it’s definitely an interesting question, but I’d probably say, go look on Skillshare, or Brilliant, or just about any MOOCs. If anyone has better tips, I want to know :) But the second thing is, you say you want to learn Fermi estimations, or general-purpose maths. I’d definitely like to learn those myself, so I have the same problem, but it actually should be very easy: there are math textbooks for bachelor students, and Fermi estimations are basically formalized guesstimates. But since I have the same problem of not actually getting very good at those, there must be a roadblock there anyway. I guess your actual problem here is the same as mine: it’s so much easier to learn anything, even something easy, when there’s someone on your back to make sure you keep doing it. If that’s the problem… well I’m also looking for the answer. But I’m sure there are good commitment devices apart from Beeminder, which I haven’t found very helpful in this case. The best would probably be what you’re actually asking for, a tutor to make sure you keep learning, but I don’t know how to find that. Maybe ask a friend to keep an eye on your progress?