One year at Carlisle I made up a bunch of "Five Cent Racing" Windshield De-Foggers for the raffle. They were made from a piece of chamois leather ( bought at Autozone - get the nice soft kind, not the el-cheapo-stiff-as-a-board kind ) wrapped around a sponge and stitched all around. It was roughly the size of your outstretched hand. I included an instruction sheet with each one telling what it was and how to use it - I mean, it's pretty simple...... You wipe it across your windshield and PooF! The inside fog is gone.
People looked at them like they were something from the days of the Spanish Inquisition. Then, over time, those people started using them and I started getting PMs and emails telling me, "Hey! I used your windshield de-fogger and the damned thing works!" And now you know how to make one, too. I have one in Pearl and another in Kelvinator and, honestly, I've never had to use them but they're there, just in case.