From Anfrey on SHO

How to polish your valve cover

1. Start off with 600 (dry) sandpaper on an electric palm/finishing sander or sanding block and sand to a smooth surface.
2. Cut 1000, 1500 & 2000 grit (wet/dry) sandpaper into 1-2" squares and soak in a bowl of water. Bowl should be one you care little about.
3. Sand surface with wet sandpaper using varying circular motions. Sandpaper will slowly loose its grit as time goes on. Use 1000 (1st), 1500 (2nd), and 2000 (3rd).
4. Surface will get smoother as time goes on. Clean cover/area thoroughly each time it gets caked up.
5. Use a polishing agent to finish surface area. I use "NeverDull", but any polish will work when used as directed.
NOTE: One sheet of each kind of sandpaper will be more than enough. If you can remove your valve cover & reinstall it when finished it will benefit your back.