It helps if your wife is already a bit of an exhibitionist, of course. Mine likes to wear revealing tops out to dinner, etc. and we always have a fun session after. I tell her about how many guys I saw enjoying her display, who didn't get to see but might have liked to, etc. Talking about her being seen is important- she needs to know you enjoy it as much as she does, that you don't think she's a bad person, etc.
During one session, I mentioned an upcoming road trip to visit her son at college. Something like, "You know, I think on our drive next week we're going to see a lot of truck traffic. Can you imagine how bored those drivers must be at times? If they got to see a beautiful pair of tits once in a while it would help a lot- so on our drive you'll need to wear a top that unbuttons or pulls down to make it easier to show them your lovely tits." (I have found some many women are more open to exposing themselves if it's someone else's idea or "command". My wife is one.)
Just the thought of it sent her into an orgasm. Now, she's only done this a few times, but on that trip she wore a peasant type top, easily pulled down. She sat with tits exposed as I pulled up to a truck and paced it for a bit, then pulled ahead. Moments later I saw every truck in front of us- maybe 5 or 6- pull almost in unison into the right lane so we could pass
She showed 17 drivers her bare tits in about a half hour. And mentioning it still gives us both a charge years later!
Best of luck with your adventure- keep us posted!