John (scdarkangel) has already written a post on how to make rivets for scratch built models. In his drop pod adventures he has been using small drops of PVA glue. When dry, they just are slightly elevated to make a dry brush possible. For my Ork army I have found this method too modest; hence I have been using a different method: cutting up tiny strips of plastic card. That is not ideal, for one, none of the rivets will be round. A hole punch makes them too big. This weekend I found my favorite method just come to me: greenstuff rivets.
I rolled the green stuff into a very long (10 inch) snake with as tiny as a diameter as you can muster. Even it out as much as you can and then let it dry overnight. You have to, because once you start cutting, you want the edges to be straight and tight.
Next day you start cutting the tiniest little pieces: they will all be perfectly round. Before you know it, you have hundreds of them (I did two snakes of 10 inches; look at my loot).
Then stick them on. I use a little hand drill as my main tool. I dab the super glue on, stick the hand drill lightly on the rivet and place it. The superglue will hold it and you can pull the drill off. I did over 150 rivets this way in 20 minutes.
Hope it helps anyone who needs it!