Putting up old crown moldings
Have you de-nailed the molding yet? If not, pull the nails through from the backside. It will leave the finish intact.

If you marked the crown so it goes back up in the same place as before, you may be able to use the old nail locations to re-nail it to the framing. If the holes are not visible since the nails may have been pulled from the backside of the trim, use blue tape to locate them on the face to see where to nail. Piloting is a good idea too.

I have even used a larger nail pushed through the original nail hole so the larger finish nail head grabs the wood still. For example if the trim is nailed with 2 1/2" nails (8D) re-nail it with a 3" (10D) or 12D nail (3 1/4").