Eye contact is everything. As in eye to bulge. Eye to ass. Eye to feet. Eye to muscles. Eye to man. Sure, it's tough to flirt when what you're looking at can't return your gaze. So that's why you need to gussy up on your gay psychic abilities.
A gay on the go should be able to flirt with a guy's ass and make that ass feel something. Some sort of twinge that it's being watched and wanted. Or flirt with a guy's bare feet and make the guy aware his feet feel a bit sore and could use some attention. Or flirt with a guy's muscular legs and make those muscles feel magnetic and powerful.
Or, hell, if the guy's dickhead is hanging out of his shorts, then you probably can use your words. Like "Hey, buddy. Your dick is hanging out of your shorts." And you can leave it up for interpretation after that. Or continue with a "Which is awesome." or a "And I'm not going to be able to stop looking so get used to it." Either way, noticing his dick at all will probably result in some sort of long term gay relationship for the following five minutes.
I'm quite glad there are no anti-bulge public ordinances or horny businessmen bulging in their suit pants would be in serious trouble. Though I wouldn't mind being the one charged with enforcing the ordinance. Perhaps documenting bulges photographically. Measuring them. Just fully assessing them and their impact on the public consciousness.
Kind of like writing parking tickets but much more subjective and obscene. It's nice to be paid to sexually harass people.
Now when a guy takes his cock out of his underwear, it changes from a semi-hard bulge situation to s fully-hard stroke session. You have to look.