Whatever you do, don't use ArmorAll or any silicone products. Meguiars makes a pretty good vinyl cleaner and protectant. Don't remember the name of it, but I'd read the label of anything to see how much alcohol it has in it. Alcohol or aliphatic naptha will dry and crack the vinyl. Silicone will migrate and prevent anything from sticking. If you should ever want to remove the dash and refinish it with a new coating of color, that silicone will cause the paint to be spotty. I've used Meguiars considerably in the past without problems. A good washing with liquid soap and water and a brush before treating will help to remove any dirt that's in the grain.
