Use your ear! Play with your nose and toes if it sounds good!
I don't mean to be flip here, but in my experience, fingering is not nearly as important as groove, swing, and pitch. If you come up with a system that works for you...use it!
Albeit, I must admit, learning technique (to serve the music!) is likely best done with a teacher who has lots of experience. That teacher may use a variety of method books to provide you with goals and insight. So, get yourself a good teacher, then explore ALL of the available literature! The bass-world is super rich with information and helpfulness!