Hey there! If you were ever looking for another way to weather your flightsuit, flak vest, spats, or even armor, I have one for you.
First thing you need to do is go out in your subdivision or local street and find a nice, fresh, oil stain. You know, the type that forms after some clunker has been sitting there dripping oil for the better part of a year.
Next, wait till a nice, hot summer day when the oil slick is nice and warm.
Don some your flightsuit (may experience strange looks as I did today ), and grab some latex gloves so you don't get oil all over your hands.
Proceed to rub latex-glove covered hands in oil slick and then apply directly to flightsuit (or other item in need of weathering).
Remember, less is more, but this technique is great and very realistic.
Hope this helps!