This is great! It will take practice -- but not because there are any moves or sleights -- just a
technique that needs to be done naturally and casually. This is a very clever technique and the
effect is a true "worker".
If you are the spectator, there is only ONE explanation other
than the premise you have an amazing memory -- which is why you really must use a borrowed deck.
Using a borrowed deck eliminates any possibility of that one explanation, leaving the spectator
gobsmacked at your supernatural ability to memorize a shuffled deck in seconds so that you can
instantly identify their chosen card.