The product that inspired this whole experiment, the Body Blur Instant HD Skin Finish ($45) has camouflaged my unsightly spider veins through four sweaty hours of dancing in a Las Vegas night club, a walk to the subway in rain and no umbrella, and, yes, sex. Just make sure you give it a good 30 minutes to completely dry before getting down to (any kind of) business, and it'll last until you wash it off with soap.