All a newbie has to do is go join a server, build a few things while unknowingly wrecking someone's work and getting disciplined ;).
and afterwards taught the basics about modifying geometry, using materials, textures. While always doing a much better job as they probably don't bother to learn it.
I do also think more of coop sessions as friend sessions, as you often make friends, get to know a few people, and knowledge is always shared between mappers.
Several such sessions are a much better teacher than your 'submission'. And even better than the manual (mostly as people don't bother to read it)
Sometimes the master on a server sets mastermode to 1 during a coop session. I've done this myself while editing cityscape.
then they create a bind (eg /bind END [kick unnamed]) which kicks unnamed players, so while knowledge is shared between players, it's not always shared with the unnamed
~Hirato Kirata