When I'm doing scraps, I mix everything up in a box as if I was folding batter, making sure that pieces cut in layers get separated. Then I take small handfuls to use as 'piles'. Grab one scrap from your original big group and match it with pile #1, big group- pile #2, etc. when one pile is empty I make a new pile that moves to the back of the pile line. Hope I explained this well enough