Its hard to have one strategy, because you can get by with 90% on one approach but theres always going to be that one guy who's pushy/talkative enough where you know the only thing that will bug him off is telling him to piss off but you can't.
When i travel abroad, homeless people are 1000% worse, and i know pretending i don't speak any language they do (i speak english and german fluently and a little french) works great, you just have to sell it, if they do catch your eye start saying something pissed off sounding in jibberish and they quit... so yeah, next time a homeless guy starts talking to you, do an impression of a subtitled movie and sounds pissed off, should work