Getting Started with Membership and bbPress

Hi,
I'm just starting a membership site - http://www.wpforchurch.com. I just have basic categories of posts and the new bbPress plugin. I'm trying to create the following levels:

Guest - can't see forums (I'd love Google to index though); can view and comment on all post categories but one.
Member - this is a registered user who can see the forums, but can't post topics or leave replies; still can't view one category.
Premium - full access to everything.

I think that I understand controlling access to the categories, but what about the bbPress rules? Does this have to be done by url?

Thanks!
Jack