I laid them flat on a table and slid them into a glass furnace. I can't remember what we placed underneath them to catch oil dribbles, but what little came out didn't touch the parts. I think we got a little on some of the oven bricks, but a quick run to 800F burned off any residual oil.
Actually, if you are going to a powdercoating shop, then you'll probably need to remove them.
Camelman