I am not sure about USA group of JWs, but in several European countries they have a pack of traveling elders who they called executioner squad. Usually, the elders in the KH reach out of to them, present them with a problematic JW, and the agreement is that this person must be DF. Usually a pair of the traveling executioners with local elder visit the targeted person and gets DFs right at the spot. The executioners return to the branch office and brag along the way who was DFs. I know people who were DFs on the JC meeting for citing older literature, for what overseer had said on the assembly, but elders disagreed, and even a person who refused to meet with these two executioners, because he did not know them and never seen them before.