I know I'm asking so many complicated questions, sorry.
So I have:
wp_ A main WordPress blog (news/pictures) + bbPress on same server
podcast_ A copy of that blog on another server (for podcast files)
bb_ And finally a bbPress used for an archive of clips that are searchable using tags
How would I get them so they all share the same wp_ user database (meaning people can login/logout/stay logged in throughout the three sites)?