CaptainMike

I'm keen to try this scotchguarding idea. People who work offshore have been doing it to fabics for years. Rather than wear non-breathable vinyl foul weather gear, I just scotchguard the heck out of a pair of jeans and denim shirt.. warmer, just as dry, doesnt trap sweat, and MUCH more comfortable.
I'm guessing it'll take 6-10 cans to do a whole car cover though and I wouldn't spray it ON the car, just in case there may be a paint issue.. I'm sure it won't hurt anything once it dries. I'm not sure how it will hold up to long term UV exposure.. It usually lasts through at least 6-7 washings though.