well, im not sure all of it.. but im almost positive at parts when he puts down the 1 card it is actually 2 cards. Stuck together. So the original 8 is actally a "5" with an 8 card underneath it. As for the slight of hand is simple cause you are not choosing any card. the card is on the top or bottom of the deck and quick simple snap.

the deck of cards actually have 2 decks in it. one red and one blue. the back of the cards have a special non slip coating on them and are paired back to back ace spades red and ace spades blue. by removing 1 card and changing it postion the blue card is revealed and no longer has the non slip properties. as a result its revealed. look closley you will see the blue deck when he splits the deck.