Personally, I break brass into 3 categories:
1) Super shiny. Head boards, foot boards, and some door knobs. Basically like chrome, but with brown, perhaps done with HSB.
2) Anistropic. I used to do a lot of plumbing. A lot of the brass that I worked with was Anistropic. Comes from a bunch of tiny grooves when the brass is manufactured (I believe). I've seen this brass in a few other places as well.
3) Muddy specular/reflection. Smooth brass, but not as highly polished as #1.
Which ever look you are going for, the first thing you'll need is a reflection map of some sort (photo or hand painted, I opt for the former). Then you'll need to distort it some how to conform to the object. Perhaps Displace or Glass. Then it's a matter of touch-ups like HSB, Grad-Map, highlights, and what-not.
The touch-ups will depend on the flavor of brass you are looking for. For example, I find Gauss and Dry Brush pretty good for #3. I've been trying several methods to get anistropic, but nothing great so far. I can get pretty close with a custom brush and Smudge, but this definitely needs refining.
Here are two links that might help you come up with a plan of attack:
Metal and Reflections Anistropic Reflections 
brassy look 
Linear Mode
