I used to have to do this way back when and now I have a (very stupid) customer demanding I send separated PDFs to them for color breakdown. Yes, I know about Output Preview in Acrobat Pro but this group lacks sufficient grey matter.
I used to have a PPD that would work for generating a postscript file. Apparently MacOS 10.8 doesn't like this PPD and my Epson SP9900 doesn't use PPDs anymore. Do you have a MacOS 10.8 PPD file that you could share?
Alternatively, is there a way to output a device independent PostScript file and distill it into separations at the sheet size rather than the default page size?