If you think about it, any Add a number effect can be looked upon as a lazy magician effect. The basis of my Synchronist act, is audience as magician. in the action of passing a billet from spectator a, to spectator b, you gain the info.. then force said info somehow on spectator b, so they can reveal it.. all you are is the go between... or force an item on a, then force the info onto b. you get the basic idea.
you simply have to take the heat off of the magician at the right moment. Something easy to do since strictly speaking a, and b are doing the effect.
you tell the spectator that you have turned a card over in the deck of cards on the table....... yoou hand them another deck..... they turn over any card...... you spread their deck..... the card reversed is seen..... you show your deck... and they have read your mind, and the cards matched.
I.D... And an ordinary deck.
Simples.

you're like Yoda.you dont say much, but what you do say is worth listening to....
Greg Wilson about.... Me.