Coming out as trans to my friend

I am a trans dude who uses he/they pronouns. I’m only out to 2 people and I’m about to come out to one of my best friends on Monday or Wednesday. He isn’t the most accepting and sometimes says offensive stuff but I help him learn what to say. He has said bad stuff about trans people but I think that’s because he’s a middle school boy. I was going to either hand him a card saying stuff about it or try to say it really casually. Can anyone help me on this? I think I want to come out but I don’t want him to get mad or stop being my friend or treat me differently.