Have a look at these antiquing solutions.
http://www.caswellplating.com/aids/metal.htm
I expect one of these will get the finish you're looking for.
You can get a flat, metallic plated look by starting with a flat metallic look before plating. You can do this by bead blasting, or scotchbriting the metal.
The finish on the part before you plate dictates the finish of the end result. Shiny parts in=shiny parts out. Flat parts in=flat parts out.