You can create Advocate teams. Often this is done by region or by subject matter.

Teams can be public or private. Public teams are visible to the Advocates and can be joined by any advocate. Advocates are assigned to Private teams the admin, and are NOT visible to the Advocate.

The admin assigns team members to the team and as soon as the advocate joins the Campaing they are automatically added to the private team.

Making a team private is easy, just flip the "Private" switch.