Oog! I understand the thumb thing. When I first started learning fingerstyle, I simply could NOT get my thumb to do the back-and-forth thing. I had to go out and get a metronome and set it really slow, and do nothing but go bong-bing-bong-bing with the thumb, over and over. Then once I got it, turn the speed up one click, and bong-bing-bong-bing until it was comfortable. Until I had worked through the speeds on the metronome and could do it pretty quickly. Then back to the slower speeds, and started adding in finger-notes. Very painful and boring work, but it paid off! I don't sound like Mississippi John Hurt or my hero Gary Davis (does anybody?) but I sound like me, and that's pretty good these days.

So, keep with it!

Alex
O..O
=o=