I tell my ukulele students if you want to develop a better rhythm hand you have to start listening to the drummer, start thinking like a drummer.
Drummers are telling you what the strumming pattern is, where the fills go, what beats to accent, it's all there just listen.
Just because you aren't the drummer doesn't meant you don't have to count.
And I leave you with this quote from perhaps the greatest rhythm hand in the business KEEF ... “Drums, eh,” says Keith Richards. “Without it you’re kinda nowhere'