I find posts hinting around the edges, but nowhere in the forums, the FAQ, or anywhere I've looked is the slightest clue on how to actually create a dynamic album. Clue please?

That is quite easy. Perfom a search and then click on "create dynamic album" on the admin tool box (you have to be logged in). Then a screen should appear where you can set some options that should be self explaining. (if not ask again)

Yep, works like a charm; I just couldn't find it without a hint.

I particularly like the ability to check which fields are searched for a given dynamic album; the ones I'm creating so far only look at tags, but I expect there'll be others later depending on location and such.

Well; hmmm. I don't understand the "guest user" stuff at all yet. If the whole gallery is supposed to be run by two people who both have full admin privs, do I need to study up on that? Or can I just ignore it (and clear out the pre-filled stuff in the dynamic album info page)?

you can read up on users here http://www.zenphoto.org/2008/07/an-overview-of-zenphoto-users/