Hell I would happily flash you anytime. I love public exposure especially full nudity but at the very least flashing my tits. But how to get a woman to do it for you other than maybe just being at the right place at the right time I just couldn't say. You can go to Mardi Gras where you know for a handful of beads you can get girls to flash. Hell in my experience girls will flash for beads most anywhere anytime actually so that might be a trick. Just throw beads from your vehicle or a motel balcony. I'm sure a few girls will respond with some skin especially at the beach or a pool where lifting their top is easy. Pools and beaches especially when few people are around is a good place as ladies may be more willing to sunbath topless especially in Brazil or other well known topless sunbathing beaches. Of course a nude beach or nude camp or event like burning man. You can do a little research and find where nudity and toplessness is most likely going to happen.
Hell just ask a woman “Can I see your tits?” Expect to be slapped more often than being flashed but I assure you some ladies will show them to you. Or when you ask do it like a joke saying how you would love to see those beautiful breasts and offering to pay her for a peek. A few ladies will be willing to flash for a price.
Of coirse you can write show me your boobs in the dust on the trunk of your car. Anytime I see that I flash the driver. Sometimes I see it on the back of a big 18 wheeler trailer and will put on a little show as I pass the truck. Good luck. I hope you see lots of tits and even fully naked ladies. Just a little planning and right places will help.