Hi Abe,
Congratulations! I also officially "came out" on Facebook recently (last year). I've tried to find the post but it's buried somewhere among the subsequent rants, haha... Basically, my "coming out" post was in the form of a shared link about discrimination against transgender women. After a lengthy rant about sexism and transphobia, I put something along the lines of "by the way, this is effectively me telling everyone that I'm transgender - hence why my gender marker has finally been set (after I never set it) as 'transgender male.' OK. Cool. Now onto other, more important things..."
I didn't get any negative comments. I did get a couple of ambiguous "it doesn't matter what you are" responses from some relatives, but absolutely no one was surprised (early transitioning has that bonus, I guess). I did get a good number of positive comments about my post but mostly no one said anything about my "coming out" because it was too much of a 'duh' moment. 😀