Gunmetal Paint for plastic

[Scrump]

I have some 3D printed plastic pieces which are white. I would like to paint them, some in Matt colours and some in a metallic finish. They are quite large so spray is better than brush.
Was thinking of using spray paint something like this:


Would this type of paint work on bare plastic? If not what sort of primer should I be applying or what alternative spray paint is best to use? Any better ways to get a metallic gun metal finish on a large plastic item?

[r159]

Halfords do a plastic primer, but their and other’s ordinary stuff would be ok, I’d go for one by the brand of the main paint you are using. Black is meant to be best for metallic colours.