Love those shirts and wanted one at one time, but my peacocking consists more of a classisist image. Tall, dark and handsome type stuff. But on to your question, as soon as they touch it, grab their hands, don't let them go, look them straight in the eyes and say "I feel violated" with a straight face. You could also say something like "How would you feel if someone came up and started grabbing YOUR chest?" or " Ooh Ooh Ooh...can I do the same to you?" or something comical like that. I would grab their hands and even do the spin move, (like in ball room dancing) and say something cocky/funny like "If you think this is nice, you should see how captivating my personality is
" If they are going to be grabbing at you just start the kino immediately because they are obviously already ok with touching you. If theirs 2 of them, get them arm and arm and just start walking and say "Let's see if this shirt can get us some drinks faster." (Not buying for them, ie say something like "I'll get the barista's attention, you get the drinks") Just take some sort of action to make them start focusing on YOU rather than the shirt. Besides, peacocking should be representative of the man... not the man himself. Back up the image you portray, and you're golden.