Started last year at 40. I just jumped in at the deep end, buying and wearing only clothes marketed to women. I started with reasonably androgynous outfits and experimented with more femme stuff at home. To start with I had no idea what I was doing, but trying stuff out and copying other women has slowly gotten me to the point where at least I'm kind of happy with how I look.
Voice also, I watched a few videos to get an idea of the basics and just started doing it 24/7. I feel a bit bad for my coworkers who had to put up with a frankly terrible voice at first. Listening to recordings I think it sounds pretty good now.
And you probably pass a lot better than you think. I've certainly had times in the past where I was obviously read as a woman and didn't quite believe it. But now I can kind of see it myself, and nobody bats an eye when I use the women's bathroom or whatever.