Trying to play guitar and plectrum banjo using Wes Montgomery thumb technique. This technique uses the fleshy outer edge of the thumb to contact the string, not the fingernail. Also it does not use a thumbpick.
Problem is, I've just started this technique and it's going to take awhile to build up the callus on the side of my thumb next to the thumbnail.
How can I play for extended periods of time with both downstrokes and upstrokes using the edge of my thumb before I build up the callus?