If you want a dusty windscreen, then you will have to mask off the area that the wipers clean. Then you spray a very thin dusty colour over the rest, sometimes even matt will do the trick, just depends on what you wish .
The Citroen looks awesome, Tommy! Love the weathering accents on the roof.
"You watch the world exploding every single night Dancing in the sun a newborn in the light, Brothers and their fathers joining hands and make a chain The shadow of the Wicker Man is rising up again......" ------"The Wicker Man", by Iron Maiden