for really stuck-on old grease i use bamboo shish-kabob skewers to scrape it off. they're soft enough that they don't scratch up metal, and much better than your fingernails. this is in combination with Goo Gone and Simple Green. I also use a brass wire brush on an electric drill, but carefully, as it can damage the finish on some metals. generally i don't use anything abrasive on cups / cones and only polished faces.