The most efficiently way to blow away the hot air inside you car is using the 12v motor based Fan,
AboveTEK has two head cooling fan specially for this purpose, check https://www.amazon.com/dp/B010CESJTC for details.

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We used the AboveTEK two head cooling fan ( https://www.amazon.com/dp/B010CESJTC ) and it works so

well to quickly blow away hot air from parking car. FYI.