My understanding is they take them to 220 grit before shipping, which is a good place to start. Inspect the thing, of course. You may find anomalies you want to clean up. Also, it might not be a bad idea to wipe it down with some water to force the grain to raise, let it dry, then give it a going over with some 220 yourself. It may get rid of some hair that isn't obvious. After that, any cleaning should be done with naphtha, which won't raise the grain.