Bluesman Vintage does something to the finish beforehand to make it more prone to checking. Their site refers to their “own proprietary mix of nitrocellulose lacquer designed specifically for authentic cold checking.” I’ve talked with John about it but I can’t remember the details. I do know it’s something he developed in-house and they use it a lot.I know of a guy that was cold checking lacquer some years ago. It was a fairly simple process of freezing a freshly nitrocellulose lacquered body & then heating the body when it came out of the freezer. The process could be repeated as needed to increase the amount of checking / cracking of the lacquer. He didn’t do any extra relic work until the body had been through the heating / cooling process.