I think actually using playing cards is a great idea. Use 3 packs of the same brand. Seperate Ace(1) to 6 of each suit from the packs and shuffle the black suits in one pile (negative), and the red suits in the other (positive). Both players draw from the same decks (3 from each) to keep things a bit random and boom! Also, 36 cards in each deck means there's 6 of each result which keeps things similar to the d6 system.
Keeps the big reveal idea and would prevent chumps like myself being tempted to cheat. Haha.