Tricks for keeping glass from fogging up racing on cold nights?

I carry a moving blanket in the trunk. Throw it on the windshield in staging and back in the pits at night. Sitting in the closed car breathing makes it worst. So I try and keep the door open. I have my ignition box in the glove box area, and the heat from it comes out the defrost vents kinda keeps it clear. Now with the new dash, no vents.