OK, I'm modifying Daniel Garcia's effect, White or Wheat (a sandwhich effect,) in order to make it simpler with easier sleights and much more involved with the spectator.
The ending is changed in this way (the beginning and middle are changed too,) but I really only need help with one sleight.
In the last quarter of the act, I place the two jokers in the spectators hand; spectator is told to keep hands closed tightly in order for no trickery and not to let anyone touch the cards. I quickly make a pass of a card into the middle face up (so it's backwards in relation to the other cards. Also to tell the truth, I don't know really how to do a pass

Edit: I found one method to do it, but it's pretty suspicious as I said before.