Many Uses of Oil Rubbed Bronze (ORB) Spray Paint--From vent covers, to picture frames, to cabinet hardware, to light fixtures--you can update without having to buy new.
To paint over ANY surface, without sanding, use a product called 'ESP Easy Surface Prep', available at hardware and paint shops. Wipe on, wipe off and paint in 90 minutes. Works well over enamel paint , without having to sand. SAVES HOURS of work. It was recommended to me by a professional painter.
Update from ssanke: The key to making the finish on your spray-painted hardware durable is to sand/rough up every surface before spraying with Rustoleum Oil Rubbed Bronze. (Best I've found for updating hardware.) Also, it's best to do several LIGHT coats or you will get drips. Let dry COMPLETELY before re-installing. I replaced many of my standard knobs with "the real deal" but I did this for larger, more costly handlesets. It's holding up great on our back door which gets *heavy* use.