Tramp, you have an unbeatable advantage that even trumps BT's two martini glasses: You clearly adore your wife. That is the sexiest, hottest thing in the known universe.
ncal: "That is the key, does she love sex and love to dress sexy and to have you show her off as men all look and drool at her. If she likes doing this then tell her how much you love the envy of the other men and how great she looks. Once you are both having a good time with sex and dressing sexy then slowly bring up swinging and how you would like to have a mfm with her and how hot that would be."
OP, please don't do this. Aside from the shitty manipulation that needs to die a thousand painful deaths, female persons are already used to having men pay intense attention to them by the time they're 14 and most still manage to never get interested in swinging. tldr: ncal is an unreliable source of information about anything.
Also, sidenote, I'm expecting a playmate in about an hour. I'm wearing yoga pants and Uggs. He won't care, except insofar as it's all easy to remove with one hand. So, the whole dressing sexy part is also bullshit.