Whoops missed this one. Pretty sure I've seen a thread like this some years ago, but whatevs.
My pseudo claw grip gradually slides towards fingertip until I re-adjust
). Ring finger for LMB, middle finger for MMB/scrolling, index finger for RMB, left thumb for back/forward.
For accuracy I also use a pseudo claw grip style. Index for LMB/MMB/scrolling, middle for RMB, ring finger and pinky for grip. Right thumb for back/forward. Can't twitch my way out of a wet paper bag.