I have a TH .40 with years of gunk on it. It runs great, but looks like crap. I don't think the extra gunk in the cooling fins helps the cooling much either. I have the engine completely disassembled and I've stuffed pieces of rags in the cylinder and crankcase to keep as much of the sand out as possible I only intend on blasting the block, head, and muffler. Is this OK? Is there any other prep work I should do?