i live in ohio so i know your pain. I have had no trouble with my car, i start it about 7 mins early so it has time to warm up (i have found the car warms up faster with the blower off and recerculation on) then i put defrost on, after my windows are done, i leave the front vent on for like 3-5 mins and my car is toasty. so i just leave def/lower vent on like 1-2 setting the rest of the time im driving.

as for some spray or wipe ect. i have found none, nor have my family or friends. The best way is to make sure your coolant is correct, cause if you are getting heat like you are supposed to you should have no problems keeping your windows defogged.