I find it hard to get good tone period. For bass I split my thoughts on tone into two setups.
Use you fingers as cleanly and consistently as possible. Let the amp do all the work. I found having a distinctive pre-amp sound and lots of overhead in the power samp stage was the key to making this sound good. My chain used to be effects to Pignose Detonator to Ampeg B 5R to Peavy cab with black widow speakers. Lots of clarity.