If you can post on the Newbie board then you can post on any of the regional boards and most of the other boards. You wont have access to the Provider Only board or the Reviewer only board (but on the latter you shouldn't have access anyhow.)

 
When you have a session you can just ask if the customer is on TER and if so would they leave a review. I suppose you could ask for TER handles in your screening (I've seen that before) and, if you paid for VIP, look at how many reviews they have done and how honest they appear (if they are all 10/10 no one is going to believe them so not credible, same if they are all 5/5) and if they have at least a couple of years history or reviews and more than 10. But a lot of reviewers on TER are a bit reluctant to provide their handle for fear of repercussions if the review is not one you like.