When playing bass, I try to use more than two fingers in fingerstyle. Im getting better with three fingers, but Im still unsure of how to do it. Should i play with index, middle, then ring... or should I play ring, middle, index?

Also has anyone else had success with using their pinky for bass fingerstyle as well?
Ring, middle, index is how i do it.

Spend an entire day just useing your ring and middle fingers.
Then if you are a mad man just use you pinky and ring.

Do that for a month and you will be a master at 4 finger picking style.
I've never tried useing my thumb much, it is very hard and kinda hurts. Funk and Jazz guys use it alot though, Victor Wooten and Billie Dickens have monster thumb attack in thier playing style, i.e double thumb plucking....

But go for it, practice it enough and you will be able to use your entire right hand.
i've seen and heard bassists use middle ring index and can hit insane beats (Alex Webster hits 276 with this technique) so those are just my two cents...