Why dont you just clean up by apparently pulling a card out of thin air?
If you dont want to do that, you can do what Keokesilverfang suggests, or what I sometimes do is in the action of showing both sides of my hand empty, I put my backpalmed card on the face of the deck. Ill try to explain that another way. I show my palm, move my hand over the deck, drop the backpalmed card on top of the deck. You can also do this under cover of the reaction of the card vanish. Just make sure that when you practice, you know which way the card is facing when you wave it before it vanishes. The way it should face is that your audience should see the face of the card. I hope this was hepful.