From what I was told by members on dsmtuners, use mineral oil or mineral spirits and a green Scott Brite pad. the gut at the machine shop showed me this bottle I can pickup from from home depot, it's a metal polish. Use with a clean rag. The polish has to be cleaned off thoroughly before use or will cause catastrophe engine failure when the polish starts moving around. I just asked how long they would take and how much it was, they said same day service with only $35~ charge. Sounds pretty close to the cost of supplies to me so they can do it. Sandblast and hot tank I believe. Or solvent tank. As long as they don't destroy my new engine, I'm satisfied.