I hate polished brass hardware. Hate it. Unfortunately, there was a lot of it in our house when we moved in. Two and a half months later I'm happy to report that 99% of it has been replaced with brushed nickel hardware. The one hangup we encountered was with our guest bathroom door knob and lock. Our house was built in 1915, and several of the doors have antique mortise locks installed. The way the locks are cut, we either have to replace the entire door or install a new mortise lock. I had no idea how hard it would be to find a new mortise lock! If money grew on trees, I would have happily gone to Rejuvenation and gotten the Putnam Classic Door Set. The money-doesn't-grow-on-trees version is this:
Yep - polished brass. That's the only finish you can get a mortise lock in these days unless you're willing to spend $200. I reluctantly bought the lock, and immediately started researching how to paint polished brass. The first step was to disassemble the lockset, soak it in a stripping agent and sand the polished brass paint off with coarse sandpaper. Once the paint was removed I was ready to prime (I used Valspar spray primer in gray.) I rigged up a stand for the lock pieces using a piece of styrofoam and toothpicks taped off with a bit of painters tape (the dumbbell was to keep the whole thing from blowing away.)
I applied the primer using multiple light coats, followed by several light coats of Rust-Oleum Metallic spray in Matte Nickel. Rust-Oleum makes a different metallic "satin nickel" spray for their Universal line, but I highly advise against using any of the metallics in this line because they have a very glittery - not at all realistic - finish (and yes, I learned that the hard way.) I sealed all the pieces with several coats of Rust-Oleum's Crystal Clear Enamel.
The door is a bit banged up from the old lock, and the finish isn't an exact match with our other brushed nickel hardware, but it's surprisingly close. Given the effort and time it took to re-finish the lockset, I wouldn't recommend painting your hardware unless money or availability (or both, in my case) make it a necessity, in which case it's a great - and fairly easy to do - project. I'd be curious to see how it would work in a different finish, especially oil-rubbed bronze.