to use cups just start the cups deamon. then point your browser to localhost:631 . there you can add your printers to cups. most printers need special drivers, that need to be installed:
* net-print/hpijs
Homepage: http://hpinkjet.sourceforge.net/
Description: The HP Inkjet server for Ghostscript. Provides best output for
HP Inkjet Printers and some LaserJets
License: BSD
* net-print/hpoj
Homepage: http://hpoj.sourceforge.net/
Description: HP OfficeJet Linux driver
License: GPL-2
* net-print/pup
Homepage: http://pup.sourceforge.net/
Description: Printer Utility Program, setup & maintenance for certain
Lexmark & HP printers
License: GPL-2
but the most important parts are:
* net-print/foomatic
Homepage: http://www.linuxprinting.org/foomatic.html
Description: The Foomatic printing meta package
License: GPL-2
* net-print/foomatic-db
Homepage: http://www.linuxprinting.org/foomatic
Description: Foomatic printer database
License: GPL-2
* net-print/foomatic-db-engine
Homepage: http://www.linuxprinting.org/foomatic
Description: Foomatic printer database engine
License: GPL-2
* net-print/foomatic-filters
Homepage: http://www.linuxprinting.org/foomatic
Description: Foomatic wrapper scripts
License: GPL-2
With these installed all printers should be usable.