I had a renault grand espace (7 seater thingy (12 windows)) all I did was put in the Silica Gel bags - the large ones from big tv and such like, I had 5 or 6 across the dashboard and a few other around the car.
The car would condensate due to my dog being in and out of the car (and the pot water dish that always had water in it, even solid water sometimes) - you know how they get.
Worked a treat never had steamed up windows, and to renew just stuck them in the microwave for 15-30 seconds open the door and let them cool before touching them.