Try to ensure that the brass fixture is truly brass rather than electroplate or plastic. Plastic produces a dull thud sound when tapped with the finger or with a metal object. Electroplate is harder to spot and may require looking up the manufacturer on the Internet to investigate any manufacturing process information located on the website.
Remove any clear coat or protective finish from the fixture with a few drops of lacquer thinner on a clean, cotton cloth. Rub the lacquer thinner with the cloth in small circles all over the fixture until you remove all the clear shiny finish.
Move the project to a well-ventilated area, such as a back porch or open outside area, spread newspaper down under the fixture to protect the work surface and put on rubber protective gloves.
Apply one of the three finish solutions to the fixture, according to the manufacturer's instructions, and allow the piece to dry, also in accordance with the manufacturer's instructions.
Finish the project by spraying the fixture with a clear, protective spray paint to protect the new oil-rubbed bronze finish.