I've also had success starting cups using the symlink method (I posted that to the blog in the comments) but have been unable to actually get a test page to print to a Laserjet 4 via Jetdirect. I defined it appropriately (I think, according to the CUPS docs) as socket://printerip:9100 and even tried ?waiteof=false and thought I was getting lucky, but it turned out someone else just happened to print to the same printer I was testing on. The page never came out.