This is how i do it. first get some whit pastels. then grind them up. Next add water untill the consistency is about modelieng paint. brush onto the model until the area is covered, but dont make it uniform, if you make it thiker in one place, and worn in another it looks ten times better . let it dry. After about a day, tak a WORN tooth brush and gentley scrape the pastel off. Some will be left and it looks great. Try this on a scratch piece first. also if you really screw up, then you can wash it off. Weathering: simple pastel shading and application to make it look dity. Hope this helps. There was an article about this in one Finescale.