Any advice on how to raise daughters to be prepared for this reality they will eventually have to deal with?
First and foremost, your daughters will look to you as their first model of acceptable male behavior. So pay attention the the things you might say without thinking about it. How you treat women, their mother in particular, is going to have a BIG influence on what they will accept as "normal". Avoid using gendered insults - in our culture, the worst insult for a boy is being compared to a girl. That's probably not the kind of thing you want your daughters to let get too comfortable in their heads, so be careful not to participate.
Let them see that you respect women as people first.
I'm not sure how old your daughters are, but teaching them to be observant of both people and their environment will also be really useful. With a military background, you have some experience with this I'd imagine. Make a game of "find all the exits" or "It's the zombie apocalypse! Where do you run for help?" when you are out and about. Be subtle, but have them pay attention to the way people interact when they think they aren't being watched, and have the girls tell you what they see. Who is smiling? Laughing? Who looks sad, distracted, busy, grumpy? How many people are wearing tennis shoes, versus flip flops? Use whatever fits the circumstances. A lot of it is just basic safety and awareness training; if you approach it in a somewhat lighthearted way, and pay more attention to the skills than the potential future threat, it will also minimize the risk of making them afraid of men in general. Kids LOVE games, and they can be used very effectively as teaching tools, because they're enjoyable.
Be polite and respectful to service workers. Because this is at least partially an issue of power, behave with civility to people who have less of it than you do. Nothing personal, but men are granted power by default, without doing a thing beyond existing. Don't be that guy in front of your daughters.
It seems that I think the most useful things you can do are going to be related to making sure that they have healthy self confidence and a good example to learn from in your behavior. I'll give this some more thought though, there are other ways to look at this.