In Versaworks, there is check box selection in the printer settings to "overprint" and a pull down menu to choose: 1, 2, or 3.
The problem comes in if you're trying to color match. Because the inks are translucent, overprinting them makes them darker as well as denser.
I've got a job in house right now that I'm fumbling around to match a spec'd color and make it dense. I'm very close by tinting it 65% and overprinting it twice... just a skoosh off right now matching the color. I don't know if that's a good way to do it, but seems to be working......