It depends on the song/tune or the sound you want.
- I'll sometimes strum down with the nail of the bird finger and up with the index. This seems to be my default strum.
- I'll sometines pick a string with my thumb and down with bird, up with index. This helps add a counter melody. (Carter Scratch) (bum-diddy)
- Sometimes I use a clawhammer type of strum: Down with the bird nail on a single string, then down again as a strum and then the thumb pulls the 4th string.
This uses the bum-diddy rhythm too, but other notes can be added with slides, hammers, pulls and drop thumb.
- I'll sometimes use a finger picking pattern using thumb, index and bird fingers in different patterns.
- I sometimes pick a single string melody alternating thumb and index.
Yep, I'm sorta the same way, coming from guitar/bass. In 1963, I used a pick mostly, always for guitar, and a lot of the time for bass. 1970's found me playing bass with my index finger. 1980's, snap and pop bass with low string thumb down stoke, and a finger to up stoke (pop) a higher string. A little later, I found that supplementing a pick with my middle finger worked for some songs on guitar. The 1990's were fingers style, with combination of two or three fingers and thumb. Less use of only playing with picks. I still thought ukuleles were for tots; didn't know better. LOL. Dang was I ever the ignorant one.
I played my first ukulele on April of last year, and was pretty well playing with Jim's style right off the bat. Had to get used to the feel, and the higher key of the ukulele though, and it took a few weeks to ween me off the guitar concept.
When strumming only though, I use the flesh part of my index finger quit often. But I do play a lot with two fingers and thumb. That is, melody lines with fingers combined with chords with either an index finger or thumb -- it depends.
In bands I've always tried not to play in another band member's space, stay in the groove, not play too busy, not play the same simultaneous chord of another band member, and that less can be more. That's when playing (usually blues and rock) in a band. I've never played in a Uke festivity or club though, and realize that the concept in those groups is probably of many people (including me?) playing chords in the same pendulum motion.
I'll be learning that experience soon though, and will give ya a report back to see if I hold back and use different strums or just hail a rhythmic pattern and strum in the same fashion as the rest. This is going to be fun for both the playing, and of the added social environment.