The simple answer is: remove the air. That's one nice thing about the mirrorless cameras, they are small and many can fit into the kinds of zipper lock bags you might have in your kitchen. Ditto for lenses. It's the air that's holding or producing the moisture as you move between inside and outside where there are extreme temperature and/or humidity differences. Thus, reducing the amount of air around the camera or lens helps considerably. (1) Bag the camera or lens. (2) Remove as much air from the bag as you can and seal the bag. (3) Give the camera or lens some time to adjust to the new environment before opening the bag and using them. Some people also add a small silica gel (water absorption) pack to their bags. There's no perfect solution for extreme environment changes, but this simple procedure helps a lot. Also, if you have control over your indoor environment, then adjusting your humidity and temperature to be less extreme compared to the outdoors helps, too. One other thing: automobiles retain humidity (or reduce it with air conditioning), too, so treat the inside of an automobile the same way you do the inside of a house.