Tortex purple... they used to be 25 cents a piece I think I'm bought 10 or 15 and I still have them. I used mostly fingers, however if I'm playing a steel string guitar I will use the tortex purple with no problem, but I also play a little bit of classical guitar, bossa nova.... sans plectrum which carries over to electric bass.
I was watching the John McLaughlin DVD years ago and his bass player was a European and he was playing thumb and two fingers and I thought that's interesting, a classical fingering tecnique on electric bass... so I employed that classical approach to my bass playing & it has been a nice addition. If I'm just cruising along it's 3 fingers tho' -- it's good to have tools in the toolbag.