Honestly, I would try breaching the concept gently at first with them. Ask how they feel about it and put some feelers out there to make sure they don't have any super negative opinions on those things.
Then go from there.
Maybe if one of your friends responds reasonably, or even positively, go from there. And be prepared for a lot of questions, because I'm sure there's a good chance they'll have questions. Some of them might even be a bit rude, but try to be patient, answer and let them know if they're being rude. Some people honestly have no idea that some questions are rude to trans individuals, so it's best to take a few deep breaths if you find yourself frustrated, and let them know calmly that those kinds of questions aren't appropriate.
As far as the other transman at your school, maybe look into joining some clubs that he's in? Or maybe approach him and introduce yourself. You don't have to out yourself immediately, but you can always try to pal around with him, and get a feel for how he is before you confide in him.
Maybe he'll be really open about it, and might even start a conversation about trans things with you before he knows you're trans? That's how I met one of my friends, actually. They thought I was just a cis guy, until it came about that the reason why I was able to give them so much information and advice on things when they weren't sure what to do, was because I wasn't. LOL
Either way, best of luck man.
Maybe even look into any LGBT groups in your town, or city? Drop by for a spell, and see if you can meet some people who might turn out to be good friends, and confidants.
