Hold on, the branch office is involved in all of this prior to the CO visiting the Congregation. At least that is what I was told by an elder in my congregation. You see, accordint to him, the elders have to meet 1 month prior to the visit to see who would qualify to be an elder or a MS. They send a form to the branch office making a recommendation of a brother. The branch office looks at the records of that brother. If the branch office is satisfied, it sends the CO the approval. Now when the CO comes to the congregation, he has to see and work with the brother. Now the CO Can make the appointment or not based on his own observations of the brother.
That's the proccess according to this elder.