I find bells usually have the desired effect on towpaths. The British Waterways "two tings" campaign might have something to do with it. I'll either use them from a fair distance back (which reduces the chicken effect), or before blind bends - one of the few situations I think they're genuinely useful.
Other shared use paths get the usual mixed reactions - it's pot luck whether they'll move to single file, hop about like chickens, or take offence. I generally prefer to make obviously 'bike' noises with the brakes or gears from closer range, as that's usually seen as non-threatening (unless your brakes squeal, in which case they leap out of the way), but will use the bell before blind bends.
Voice I usually reserve for other cyclists - "passing on your right" - or horses etc.
It doesn't really matter that much anyway, as so many peds are going to miss auditory cues regardless, either through hearing loss, use of phones/music players or being distracted by their conversation.