I am not really in to gaff cards byt i got a doublebacked card with my shadowmasters deck so i tought i could use it but i dont know any tricks that uses a doublebacked card, so i tought i ask you guys.
Daniel Garcia has an excellent All Backs routine that you should check out. It's alot different than other routines of its kind. I think it's on one of his Project DVD's.
I find using a double backed card makes a great start to an ambitious card routine. Place the selection face up on top of the double backed card, turn them face down with a double lift, place the double backer in the centre and show that the selection is back on top.
PM me if you want to know the details. I don't know if this is published anywhere, and so I have devised a method myself. You run the risk of being caught, but when you pull it off, it's a freaking miracle!!!