Problem with a deck of cards

Without wanting to discuss an ongoing empathy game, I want to submit the clever LG community a problem I have.

Beloved regretted Martin Gardner designed a clever trick based on the fact that if you deal a complete deck of cards, putting 1st card under the deck, then showing the next and continuing until last card ; you can devise which the last card will be by rotating the binary digits of the number of cards in the deck left :

example for 52 cards (110100) the last card will be the 41st (101001), but I can't find an easy way to guess for the penultimate card.

Also to do the magic trick, I count 11 cards on the bottom of the pack and try to convince the victim to put his card on top of those, but is there a better way to exploit this trick?