I started doing this with KK long before the hot wife thing got rolling. Usually, it was prefixed with hot pillow talk about KK dressing sexy and picking up some stranger in the hotel bar, taking him back to his, or her room, and fucking his brains out.
I tried incentivizing her by sneaking hot outfits into her luggage; "fuck me" heels, lingerie, stockings, etc. Over time, I added condoms and lube, discreet sex toys, sometimes sexy pulp novels or Penthouse Letters, Variations, or some such.
She responded to these attempts at corruption with a stern "It'll never happen." Years later, I found out KK was acting on these fantasies, realizing them in clandestine hook-ups during her business travel. The confessions were extraordinarily hot!