So you want to keep the brushed metal look? That's easy!
Have it powder coated with clear. You can use clear powder coating over any raw metal. You can also add pearls, metal flake, etc. There must be someone around you that can do powder coating.
http://www.eastwood.com/hotcoat-powd...r-powders.html
This video shows how you can polish something and then do some artwork using decals. They polished a bat and then added some color but for your case you would just get the metal brushed and then clean it and powder coat it clear.
http://www.youtube.com/watch?v=3yBf-cPHs7o
There is also one other way -
If you have an automotive paint store go in and tell them what you are doing. They can show you some things. Ask them about using just the "toner". It's not clear but it comes in lots of colors. It's fairly transparent so you could keep the brushed look and spray a cool color over it and the brush markings still show through. Then you can clear coat that and it would look awesome.