We travel a good bit in winter and get the same morning windshield fogging you mention. What I do is use a hand towel to wipe windshield and side windows, then place one of our space heaters on the dash set on low heat to finish the job. By the time I finish other duties to get on the road, all is clear. I get a few looks from campground walkers, but it gives them a little added feature for their morning walk.