I usually ring the bell 3 times when I'm passing. I find that gives them a better idea of how fast I'm coming up. Usually I'll slow down a bit if there's more than one non-cyclist or they're with little children or pets.
MUPs here are about 6ft (2m) wide most of the time. Some places are really wide while other spots are slightly narrower. If there are peds or bladers blocking the entire lane up and oblivious to the fact that I'm passing I usually yell 'coming through'. Although, occasionally I've been tempted to yell 'AHHHHH! outta the way, no brakes! no brakes!'