At the time I came out I was on a residential apprenticeship, similar in a way to school/college I suppose. There were the 200 apprentices I lived with, HR/admin staff from my company, a couple of instructors from the company, as well as a contractor company who provided the instruction and residential support.
I came out to a trans woman who was an instructor for the company first off, asking for a bit of advice with who to talk to. Then when a letter came through from my gender identity clinic without any name on the envelope and was opened by admin to find out where it was supposed to go, I panicked, and went and asked her to tell whoever she saw fit so that it didn't come out as a result of this letter, and I knew who knew and who didn't.
Me and my manager discussed how we saw best to handle this. He told the relevant HR staff for both our company and the contractors so that they could start working out how to change their records and anything else which needed to be done first, and then we worked out what we would do with everyone else. Neither of us were keen on doing it via email, as the main thing for me was to make sure that everyone knew at the same time, so it wasn't being passed around the rumour mill, and end up as an entirely different story by the time it got to the last person. I suggested telling everyone in the meetings we have where everyone has to attend, which he thought was a good idea, and then I realised just how difficult that would be, and asked him to do it for me, which he was willing to do, and could see the merit in others seeing that he had my back on this. The only other option was to go around each class and talk to them, with my manager if I wanted, but again, there would probably be rumours before I got to the last class, and I knew my nerves would be shot after the first class.
The day before the meeting the teamleaders of the instructors were told, and at lunchtime there was a meeting where the instructors were told, and explained that from the following day on I was to be treated as male. Just before the meeting the residential support staff were told, which I found kinda funny, as they all automatically came and boxed me in incase anyone reacted badly to it. Then it was back to the accommodation and moving out of the female rooms. I went to McDonalds to use the toilet the first time I needed it, so that people had a few hours to get their heads around me being male before walking into me in the bathroom, but after that I used them as normal and everything was fine.
It's been just over 6 months since I came out, and I'd not change how I did it at all. Obviously it's not going to be an option for everyone, and it was the most terrifying thing I've ever done just to sit there and hear the thing I'd tried to hide for so long, and had just cost me my family, be told to everyone else I knew. I took my pulse just before he started his piece on me, 192 bpm, and then I took my pulse in the plane (I hate flying too) just before I did a skydive, and it was fast, but now where near as bad!
I cut off all ties with my former name as immediately as possible. My email address was changed within a day or two, my security pass was swapped the same day just after the meeting, the HR manager very gleefully showed me that they'd made a new copy of the massive laminated list of apprentices the next day, and all the other things which slipped through the net were caught very quickly. There was no umming and ahhing from those higher up, so my peers knew that it wasn't acceptable to do that either. My surname is pretty uncommon though, so anyone who might have forgotten who Alex was would still recognise me easily.