I did this yesterday. I took 3 rifles and rotated. I also use two fans, one is battery operated, really pointed it at me. The other goes up the chamber, works really good. If only testing 1 rifle, maybe take a .22 to pass the time.
I did see a shooter using a cold towel laid over his barrel. It was a composite stock, not wood. Take a small ice chest with ice a water, wring the towel out VERY good.