I guess it's easier for some than for others. I have always been a bit of an actor, doing regional and foreign accents and pitches. My natural voice and singing range is from bass to mid-tenor. A couple of the YouTube videos I watched a couple of years ago pointed out how to start at your natural upper range (without forcing it) and practice. Then, after a bit, to go up another notch. If you (at least for me) have gotten used to the upper range, you can then go higher without forcing it.
It also pointed out the timber of the female voice (as well as slight breathiness) required. It talked about the average range (pitch) of the female voice and how it is only a few notes higher than the average range of the male voice. I started noticing the pitch of the lower-voiced cis-women and realized that it was lower than my upper range (without getting into falsetto).
That's when I realized it was doable for me if I practiced and also paid attention to the little things. (It's about vocabulary choice and intonation and tentative languaging in addition to the pitch.) I took their advice and started recording my attempts. It clearly wasn't convincing at first, but I got better over a few weeks (to a few months).
I'm not en femme often enough for it to come out without thinking of it (to start with) but it doesn't take much, now, for me to sharpen back up enough to revert to doing it as second-nature. It helps me to replay Marilyn Monroe in my head briefly to get the feel for it again and then it can start flowing out. I have noticed, however, that my vocabulary has changed to more feminine, even when I am in guy mode. (For instance, I now say "tummy" instead of "stomach" or "belly" or "gut" without thinking about it. And there are lots of other instances, as well. The funny thing is, if guys hear that when I am in guy mode, most of them either don't think anything of it or they think "he's gay", not "he's trans". And most of them are MUCH more accepting of gay than of trans (at least these days).
In essence, a lot of being able to carry it off is not about the pitch, but about a lot of the other aspects of it. Especially since there is so much overlap between the average male range and the average female range.