I gave up the pick in favor of the thumb a few years back and have been happy with the results. (You can check out
Kanaal van paulkogutmusic - YouTube
most videos are with the thumb.) I recommend studying any of the available Wes Montgomery video footage and really paying attention to his left hand fingerings, he plays across the neck diagonally rather than sticking to CAGED box patterns, and I think that has as much to do with his 'sound' as the right hand thumb. John Abercrombie has been using the thumb for the last 20 or so years, he's well worth checking out. Other players I'm aware of are Jimmy Ponder and Jim Mullen. Good luck!