Thanks for the link Several! Yes, that is a useful tutorial with several methods of painting in rivets, but none of them are as simple as the photoshop method in Adlabs' tutorial, where you click between two points and automatically have the rivets perfectly spaced.
It seems that this is one area where PSP isn't as good as PS? Which is a bugger because I was perfectly happy with PSP until I saw Adlabs' tute