When I go out passing as male I generally get mistaken for very young. I don't get carded because people assume No Way am I 21. I'm actually 24 next week! It's the baby face (and maaaaaaybe the height? I'm 5'5"). I'm not ready to do hormones or anything medical. But maybe someone has some makeup tricks to add on the years?
Ah, yes, the dreaded "Peter Pan Syndrome." This is a common problem, and I don't know if anyone has managed to entirely solve this, beyond simply aging up over the years. Facial hair really helps, if you're able to grow it. Rogaine helps with this, even before T. Just don't use it if you have cats. Rogane is deadly toxic to cats, even in small amounts or incidental contact such as a cat sleeping on your pillow after you. A short, conservative and traditional haircut - a "businessman's cut" or a "gentleman cut" helps with a more mature look, especially with a "hard part" (a type of side part). Longer hairstyles and modern/stylish/edgy cuts make most guys look younger. Clothing-wise, again, stay away from modern/stylish/edgy fashions, stick with traditional classic stuff, something you'd expect to see on a 30- or 40-year-old, not a 22 year old college kid or 17-year-old high schooler. Eventually you'll grow out of it, but from knowing a lot of trans guys, it's likely you'll appear 10-15 years younger than your chronological age until you hit your 50s.
Hah, I actually played Peter Pan when I was 16! I do have cats so rogaine is out but I'll give the haircut a try. Right now I have a buzz cut, which maybe plays up the baby-face.
Some people will just always look young. I have been on hormones for aroung 5 years now. I look like I am 16. I've just learned to go with it. I'm actually 26. It can be annoying at times, but I've just made peace with the fact that i look way younger than I really am.