Me too...don't ever have thumb pain or numbness...or
callouses. Not sure what I'm doing different. I play most
days for an hour or more and sometimes on the weekend for
a few hours at a time.
Alex,
The right position should help you (i.e. 45%, etc.).
By the way, you never have use the #1 top button. This is a redondant note that in the past would be used as a frame of reference to tune the accordion. #2 button is much easier to reach.