Pour about 1 tsp. ketchup from the bottle onto a cleaning rag.
Rub the ketchup over the entire brass frame, leaving behind a thin layer of the ketchup. Let it sit on the brass for 15 minutes.
Run a clean rag under warm water, and squeeze out the rag.
Wipe off the ketchup with the rag, and continue until you get all ketchup off the brass surfaces.
Polish the brass by wiping with a clean, dry cloth. Rub in small circular motions while wiping to buff and bring out the shine of the brass.