+xYou would get a matt finish from a matt mould, however the finish is not always even so very rarely does it look great. Also many release agents will add a gloss finish to the surface thus ruining the matt effect even more.
The most reliable way, in our experience, is to use a matt or Satin lacquer sprayed onto the part after manufacture. The lacquers generally go down very evenly with a good even finish to them. Also most lacquers are UV stable so you have the added benefit of further UV stability.
Thanks Warren, I'll try that!