I would like to add gaff cards into my show is there a book or dvd that teach me how to manage gaff cards better in terms of adding them into my deck and removing them.
Usually this depends on the context.
In some tricks (e.g. Johns Bannon´s classic "Strangers Gallery") it´s a built in logic that you end with removing the gaffs from the deck.
You can leave the gaff in the cardbox and then put the deck into the cardbox after a trick, do something else and then take the deck with the added gaffs out for another card trick.
You could also select the tricks in your set in a way that the existence of the gaffs in the deck doesn´t matter for preceeding or suceedeing tricks (similar to Denis Behr´s "finding you way home"-concept for memorized deck work).
Or just switch the whole deck.
Or the obvious one: Palm the gaffs off in the offbeat after the trick (or add the gaffs respectively)
Just figure out what you want to do with gaffs first and when that´s clear you´ll probaly figure out a way to manage them.