I did this recently, back in March. I kept it short and sweet. Wrote a letter directly to an elder whom I had respect for as a friend and for being a decent human being. It's not their fault they are captives of a concept the same as we were before we found ttatt.
I didn't hear anything for a month so I called him and asked him if he received my letter. He said he did and was hoping to discuss it with me. I asked him if he wanted to discuss one on one and he said no, with another elder. I said I wouldn't and he asked me to call the other elder to confirm my letter. They announced it that week.
I think they are checking if you are depressed or under stress or something but they almost don't take your word for it when you write a letter which is strange. Maybe it's different elsewhere but that was my experience here in Rhode Island circuit 1.
I'm not concerned with if I'm playing by their rules or not. I just didn't want to be officially a witness. I formally got baptized and wanted to formally get unbaptized, so to speak.