I have xfce. More software will work with LPRNG than with Cups. So that is what I use. But Firefox only gives me print to file as a choice. So where and how do I modify Firefox to recognize the Postscript printer available on /dev/lp0?
There's xfprint, but I personally haven't used it. I'd check that out and see if it helps any, if not google "firefox printers" or "firefox printing" and see if you can come up with something.