Build Permissions - cant find a working solution

Hello guys,
im just setting up a small server and im running into a little problem with build permissions. Ofcourese i already read the forums, used google etc.
Im using the following plugins (for this problem fitting):
Multiverse, GroupManager, WorldGuard

I've created different world via Multiverse (2 Worlds interesting for this topic)
Also I used GroupManager to setup some groups (2 Groups interesting for this topic)
And of course for all protection stuff i want to use WorldGuard.

So what i try to archive is:
- Permission group "Guest" has no build permissions at all in any world
- All Permission groups have no build permissions in the world named "plains"
- After assigning a region to a player in the world "plains" he (and only he) can build in this specific area.

GroupManager includes a boolean property called "build" however, it looks like WorldGuard doesnt realy read this.
I tried to use the _global_ region in the main world and set build to false with "-g Guest" however it doesnt knows the Guest group.

edit: Found the first solution so the problem which is left:
How do i get WorldGuard to forbid building globaly for the Guest player group? (has build: false)

Thanks to everyone providing me usefull informations.

 

when setting up the permissions did you include the world name?
PEX example: pex group Admin add build.example plains
maybe there is such command for Group Manager?

 

Nope, because all worlds share the permissions from GroupManager. i used the mirror option provided. I think its more of WorldGuards task to do those two things - its build prevention, nothing more

its basicaly what this plugin does: http://forums.bukkit.org/threads/6771/
If WorldGuard cant do that, ill use that plugin and the problem is solved. But i would prefer not using an extra plugin for that.