David Hamburger doesn't do one on one courses as far as I know, but does do an online course where he takes a group of students with online lessons through one arrangement per month with the goal of learning to improvise on the tune (while playing solo fingerstyle). I was a member for a few months, but life got in the way. I would love to sign up again. See
https://www.fretboardconfidential.com/ for details.