My obsession with ink separations is finally spitting out some useful results. In the sample below we start with a two color image. That image is then screened onto a black shirt, first with white ink, and then with a layer of red ink. Of course the image can't be replicated with so few (one) color, but the program is at least not spitting out a black-only image.
Note that this is designed for opaque inks, so if I'd made the first screen red and the second one white, it would have spit out very different results!