Try giving a primer on gender while handing change to a cashier. Or piping up about your pronouns in a lecture hall filled with several hundred students. There are some situations where I can explain things in private, like with teachers, but then you have to hope for the best with the teacher’s reaction. I had a really wonderful creative writing teacher that I loved a lot, and I explained my gender and pronouns to her pretty early on. It still took her a full year to stop using the wrong pronouns in class, and it took me a full year to feel comfortable correcting her in front of thirty or so people who didn’t know I was trans.