I know there are at least two of us and must be more here on UU who regularly accompany uke groups using our u-basses. Please comment in this thread if you are a uke group u-bass player.
Currently I am accompanying four ukulele jam groups that meet regularly. One of those groups also does some gigs and has additional rehearsals. I'm not really a bass player, and I've had no training on bass at all. My bass playing derived from being a guitar player who knew the notes on the fretboard.
It seems to me that playing uke bass with uke groups is a somewhat specialized kind of bass playing. It's sort of akin to playing bluegrass bass. My style is heavily influenced by bluegrass jams I've attended to play bass. My playing involves too much root/five and I'm trying to branch out and to try new rhythm patterns. The key though for us uke types is to fit in and not overpower or throw off the group.
I have never played uke or bass with a uke group, but I do play my ukulele with rock, funk, blues, etc, both acoustic as well as electric.
I also play a bit of bass.
If you want to expand your bass skills, practice your major and minor pentatonic scales. Practice with a metronome. Practice you major and minor pentatonic scales. Practice with a metronome. Once you get yourself well versed in those, your ears and your sense of the music will tell you what will sound good for the ensemble and songs you're playing.
BUT,,, don't be afraid of 1 & 5. Coloring your line is great, but bass players have survived for millions of years on a steady diet of 1 & 5.
Remember that being a good bass player is more about rhythm, so if you want to be more solid and interesting, work on the sharpness in your timing, both in your right hand and in the way your left hand supports and affects the rhythm.
Practice you major and minor pentatonic scales. Practice with a metronome.
Also learn other people's bass lines. Even if you don't remember them two days later, playing other people's lines will build your understanding of how bass works.
For acoustic or lower volume situations, I play through a Roland Cube 30 Bass. for the size and price, it has a pretty darn good sound, at lower and higher volumes. It has some cool effects onboard too.
My U-Bass is a Kala Rumbler, I also play a Fender (MIM) Jazz fretless and a mid-80's Peavy Dyna Bass. Though I don't think I'd play the Dyna with a uke group
