Progressive Weathering

I try not to weather two cars in the same manner, so I use a technique I call "progressive weathering". It's not original - I read about in a magazine a while back. Here I had 4 identical cars to weather. Made one weathering pass to all four, then set one aside as done. Then another pass to the remaining three, then set one aside as done. Continue in this manner until all are done. Here are the results. Least weathered at the top - should be obvious! This was a lot of four Tyco "Old Dutch Cleanser" cars obtained used from eBay.