Wash the frame thoroughly using a gentle liquid dish detergent. This will remove dirt and debris from the frame, which makes polishing the frame easier. Allow the frame to dry completely.
Lay a plastic tablecloth on a table. This will protect the frame from being scratched while you are polishing it. Ideally, you should work in a well-ventilated, covered area. A room with a window open is a good option. Place the frame on the plastic or cardboard.
Remove any paint or other markings from the frame using paint thinner. Pour the paint thinner onto a clean towel and wipe the frame. Rinse the frame off and allow it to dry.
Sand the frame using wet 320 grit sand paper. You should make sure that the sand paper and the frame stay wet any time you are sanding. This is called wet sanding. You will need to turn the frame as you work so you can sand all of the frame.
Continue to wet sand the frame using 400 grit, then 600 grit, 800 grit, 1200 grit and finally 2000 grit sand paper. With each grit, you will remove the scratches made by the previous grit. Take your time to ensure that all imperfections are sanded out. By the time you finish sanding with the 2000 grit sand paper, the frame should be as smooth as glass.
Polish the frame using a clean polishing pad and a blue polishing cream. Once you have polished the entire frame, it should be very shiny, almost like chrome.
Wipe the frame off with a flannel cloth to remove smudges.