i used some wet n dry sanding paper dragged in the same direction over a delorean plastic model years ago,then sprayed silver over the top. it came out very well.
i intend to use the same method on an iron man helmet when i get round to it
a guy down the pub said his brothers girfriends uncle once knew a guy that thinks he was a painter on the film said he thought it was not hand brushed.
but he did have a couple of lagers so he may be wrong, plus he was a crack addict.