Here's a better view of the faces. Of course, this isn't really going to come together until I lay down the color.
So I wound up doing the selections by using an eraser set to airbrush and going around each piece, once against a black background layer, once against a white -- each revealed scraps that didn't show against the other. Since this image was, as I said, 20" x 48" it was quite the little time-consuming process.
Which brings me to the next chore -- going over the whole thing using the rubber stamp tool to eliminate black spots and rings that make it obvious that this was based in inkblots. I debated this -- in the first piece in this series I left them in (there were some other artifacts generated by the process of making inkblots that couldn't be eliminated as well), but in this case I think they'd look too ugly to justify. Oh, well -- labor is part of the process.