Well, I honestly don't know of any GOOD tricks you can do with double backers, but I do know of a few. You can have the DB at the bottom, force the top card, cut the deck, show there's one card face down, perform a DL and there you have an adequate trick. Although, you can try to merge two cards into one, in one way or another. That would be and amazing trick, but I haven't figured out a method.