It's Murphy's Law of a "quick shower"--your bathroom mirror will take twice as long as you spent in the shower to de-fog enough for you to actually use it. The more you wipe at the fog, the worse it seems to get. What's a hurried gal (or guy) to do?
The next time you clean your bathroom mirror, after you wipe off your cleaning product of choice, apply a layer of inexpensive shaving cream to your mirror, let it sit for about 3 minutes, and then wipe it off. Your mirror will stay amazingly fog-free and ready-to-use for 4-6 weeks.