Abrasive snap caps.
Somebody enterprising can sell them as a kit, with a naked replacement firing pin just in case the snaps caps damage the original.
Who needs expensive machinery? Just give it a quick rub on the sidewalk and gtg. Not to mention it will wear off under normal use. I would bet within 1000 rds.
As part of being a responsible gun owner, use a fine needle file to remove any burrs from the firing pin. Don't want anything there that might cause failures.