Brass is a reactive metal and many fabricators offer a few finishes. The most common, and best choice, is the Non-Directional Matte finish. This allows the metal to adapt and react to its environment with a matte finish that will quickly react once in use. Please understand that brass will always want to react to its environment and spots may form regardless of your coating or finish.
Patinas add a base color or pattern. This is an additional step that mimics what will happen naturally. Likewise, after the patination process, the metal will still react to its environment so keep in mind that the patina is not permanent.