I have had frame filers say they won't let an engraver touch a receiver until they, the filer, prepares the surface. I have had engravers say they want to prepare everything themselves. Some case color guys want to prepare the surface. Your job is to pick an engraver who thinks he is the greatest polisher in the world or find that greatest polisher before you send it to the engraver. Waiting until it gets to the case color guy is too late if your gun is freshly engraved.