Yes you can strip your brass fixture, and antique it. First you must check and see if you fixture is actually brass. See if a magnet sticks to it. If it does, you have plated steel and Antiqueing might be a trainwreck. Second if it is not magnetic, try and score an inconspicuous area with a scribe and see if it comes up a brass color. Sometimes brass plating is put over "potmetal". If it is brass, then lacquer thinner should remove a typical coating without harming the structure. If it doesn't, a more nobel stripper may be needed if it is powdercoated.