Use lots of soap and water----also use STAINLESS STEEL blades(they won't scratch the window).I've never had a problem with the defroster when using both!!!!
I got the tint on my back window to peel right off. I then used lacquer thinner to remove the glue residue. I took out the rear seat when doing this in case I spilled any of the thinner. I didn't use a scraper at all.
I recommend doing this outside as the fumes are pretty nasty. And don't smoke cigarettes either.