I accidentally developed a really effective way to deal with strangers hitting on me, which is to stare at them with a completely unchanging, neutral expression and ask autistically, "are you trying to have sex with me?"
I don't mean this re: catcalling, which usually happens as I walk by, I mean when I'm doing something like standing outside a store waiting for a friend and the person actively approaches me.
I've got a pretty good feel for like.... empathy-ness in people? Sometimes when people approach, you can tell they don't give a shit, or are mentally unstable, or are obviously not sensitive to my feelings or boundaries.
If they do give empathy signals then I'm really friendly.
Honestly, to be on the other end of that that would be the funniest thing that happened to me in pretty much any given week. I wish more women did this.