Seattle Advanced studying/tasting groups?

Hello,

I have just passed my Certified and I would love to keep studying to prepare for the Advanced exam. I am not sure how to make a plan. I was told it is harder to join tasting groups at this point?

As far as theory, are the study guides from Guildsomm a good resource? Compendium?

Any input and piece of advice would be very much appreciated.

Thank you

Silvia