I've found in several places that the antidote to being called "sir" is...boobies! Anywhere I've been called "sir" when I was wearing a T shirt and smooth bralette underneath, on the next visit I wore a deep V neck top and a push up bra, and -- no more being called "sir!" I don't get called ma'am either, folks just drop the gendered appellation, but that is far better than getting sirred.
Having the girls visible seems to do quite a number on guys' instincts for some reason. I've found nothing else -- butt, legs, heels, or hair, even -- seems to make as much a difference in a guy's momentary evaluation of gender the way a pair of bewbs will.
I don't have enough data to say whether a leg show will have equal effect, but I have noticed when wearing shorts out and about in hot weather, the shorter they are, the more likely I am going to be gendered female, especially by other women.