A while ago I stupidly drove for about 500 miles with a broken brake disc. When I got out of the car I noticed the wheel trim was brown and thought nothing of it. Anyway whilst cleaning the car today I have noticed what can only be described as iron fillings stuck down the side of the car. They are rough to the touch. and if you look really closely you can see them. After an hour scrubbing they are not shifting. The point of writing this is I'm hopefully selling the car in a few weeks and I'm thinking this will affect the sale. Would claying the car work as they are stuck on. Its hard to describe. Any advice or help appreciated and hopefully nothing along the lines of what my boss said "you need something with a long hydrocarbon structure". WTF does that mean?