Thanks for the comment guys,
one thing I have learn from armour modelling is to let the paint finish take care of itself, what I mean is I don't worry about whether an item is totally matt or semi gloss or even glossy unless it's cloth material like harnesses. I usually paint with a matt finish and let my weathering techniques create subtle variations to the sheen of the paint, this creates interest in areas of single colour. I do use oil paints a lot in my weathering, I love the way you can create shadows and different sheens to items to differentiate between materials.
I'm working on the lMG08's at the moment and I purposely have not weathered the cooling jacket as I want to create contrast between the steel body of the gun and the more fragile sheet metal of the jacket itself