How do I block access a sub-blog to all but subscribers?

I would like to regulate access to specific sub-blogs on my WP MU with BP so that:

* membership level MEMBER can access sub-blogs A & B
* membership level VIP can access sub-blogs B & C
* strengers can access no sub-blogs

I have been reading the forum and am rather confused.

1) Can I use the Membership plugin to regulate this?
2) Must I use @Jonathan 's suggestion to share tables across my network? (see for example: )
3) Should I install the "Multisite privacy" plugin? Would that help?
4) Are there other ways?