I try to initially use a respectful but firm conversational/pleasentries kind of tone in these situations. Beyond the initial contact, my tone changes dramatically. Fewer words and a flatter, more assertive tone.
Initial pester: Eye contact and "Not today. Have a good one."
Further pestering: Attempt to put a physical barrier between us, make eye contact with a more serious face, firm posture, a palm and "I said no. Now back off, dude."
Yet further pestering: Depending on circumstance, become scarce or stand my ground. In either case, a commanding voice is in order. If I have to use a commanding voice, the police get a call -- the guy's harrassing me or attempting to initiate a mugging.
We got lots of practice with this in Iraq. You must remain firm and respectful, but never leave yourself at a disadvantage. Many times, in the sandbox or here in the evergreen state, the necessary deterrent was body language. You can say a lot with your posture, hands, facial expression and eyes, and physical orientation to the potential aggressor and your surroundings. If you look like you're getting serious and defensive, but self confident... they usually back off. They are typically watching your behavior just as much as you are theirs.
In these kind of dynamic scenarios, the only thing we can do is continue to gauge the situation, maintain situational awareness, and listen to our gut. If at any point we feel in danger, it is not unreasonable to take a defensive posture and put hand to weapon. We don't necessarily need to draw, which could be construed as brandishing, but reducing our presentation time could be a good idea. No need to telegraph. Turn your gun side away. Keep moving and be aware of your surroundings, and any other people around you.
Don't be afraid to listen to your gut. Don't let people bully or harrass you. Respond to strange people doing strange things assertively, immediately, and in no uncertain terms.
If it gets rushed, you can blurt something like "Hey, you're freakin' me out, dude... back off... NOW."
I warded off a cigarrette bummin' gas station thug one time. It was obvious that he was using the panhandler's come-on. He didn't seem like he really wanted a cigarette. My only words were "I don't smoke." When he kept coming, and mumbling something about a cigarrette, the flag went up in my brain and I gave him a stone-faced stare. He sized me up, noticed that he couldn't see my hands and that I was serious... and froze in his tracks. He had this look of recognition on his face, like the realization that he'd been busted. Then he said "whoa... it's cool man... " showed me his palms and backed away. On that occasion, it was all about what I didn't say.
I kept an eye on him, finished my fuel-up and got on down the road. I don't know what he wanted, but I'm pretty damn sure it wasn't a cigarrette.
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