When the figure is fully painted, I apply a coat of Dull Cote first, followed by a very light dusting of Testors semi-gloss. This give the figure just a tiny shine, enough to make it look like manufactured plastic, preserving the illusion!
[Update] Testor’s semi-gloss has become difficult to find. I’m not sure it’s even manufactured anymore. I’ve switched to a light coat of Testor’s gloss, and it works just as well.