Norway is not what it used to be in terms of winters, and today we've hit 7C in the Oslo area. I've decided to wash my Model S by hand, and have found out that some surfaces of the car are rough. It is probably from all the salt and s**t you get from the roads. It can mainly be felt around the tires and on the rear of the car. How can we get rid of that layer of roughness without damaging the paint? Any tips?