So, reading through this thread I've had to say WOW! Not in a good way. The basic question here is "How do I tell my wife", that really depends on the wife, the attitude, or as Rachel said: What is your wife like? Is she religious? Does she have friends in alternative lifestyles? Has she ever jokingly offered to put makeup or lingerie on you? What are her parents like? All these and more will help you work out whether and how to approach her with this.
What shocked was the undertone that this was an obstacle to be conquered by any means necessary, all I can say is wake up and smell the coffee... What we are doing runs contrary to everything that is considered normal in our civilization, our wives are raised to see men in a certain way and guess what, we don't look like that when we're in a dress and makeup. I love my wife, and I know she loves me and this is still one of the most difficult things we have had to face during our marriage. Having said that, I think that it's important to let your wife in on the secret, because by excluding her you are doing her a disservice and the lies and secrets will eventually be found out. I won't lie, your wife may not want to have anything to do with you, knowing that you dress, on the other hand she may be very supporting, or any of a million permutations in between... Good luck, whatever you choose.