I thought this would be hard but essentially it was very easy - I guess and seemed to get it right first time.

You don’t need to install CUPS as the SUNWhpijs package already supports Sun’s own print system. Simply run:

/usr/sadm/admin/bin/printmgr

… as root, choose PRINTER->NEW ATTACHED PRINTER from the menu and then add the printer. I found it to be attached to /dev/usb/printer0 and I had to claim it was an OfficeJet 6110, but essentially everything worked perfectly and seconds later I was printing in colour on A4 paper.