I never use finger or thumb rests. If they come on a bass and are in the way - I remove them, otherwise I leave them for vintage reference 'looks'. I use my right-hand pinky as a stilt to ground playing/articulation, usually right behind the bridge pu. Wear-marks there confirm. I have a pic somewhere that illustrates this but it would be exhausting to find it amid thousands of pics.
I noticed a funky wear spot on a bass I bought between the bridge and the output Jack. Asked the seller and that was where he anchored his pinky as he hammered away with a pick.
Me personally, my thumb kind of wanders wherever it sees fit. Not necessarily anchored but not quite floating string to string anchored either. And I couldn't put a rest anywhere cuz I like to move towards the neck or towards the bridge depending on what I'm going for tonally.
