You may want to check /usr/share/examples/supfiles, which contains a basic setup.

Check out that part about tracking -current with sup / cvs / 'sup into cvs'
at the Netbsd page [www.netbsd.org/Documentation/current/#using-sup-into-cvs,
which contains information you might not need, as you are used to using it
with FreeBSD, nonetheless, it doesn't cost you much ;)

There is a list of available tags (together with explanations) available at
/usr/doc/README.sup, from which you can choose to build up your local source
tree as needed [common kernel-sources, i386-platform sources, gnu, release,
etc, blabla sources, choose what you need ;) ]

Erm, might be I oversaw something, but digging through that you'll find pointers
of what you are lacking. Have fun,

--
Martin Weber