Since you can't add layers of materials inside the glass or run lines of heated metal to heat a wind shield, you must use your inside window defroster. If you had a hot wiper blade that didn't crack your window you could use the cold temperature wiper fluid and then swish it around with heated wiper blades for maximum speed of defrost and then you can turn your defroster to a different setting to heat the inside to help defrost the rest of the windows.
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