So my 76 Custom is filthy. A lot of sweat and grime built up on the finish. The nitro also has hairline cracks in it all around the body and various checking too. I’ve read Naptha is the way to go but I’ve also read about being careful if the finish has cracks in it because the Naptha can seep into the finish and mess with the wood/ discolor it. Should I go ahead with the Naptha? I don’t want to mess with the patina, just get the grime off. Thanks.