Enamel Product.

With this enamel product the modeler may easily represent streaking dirt effects on ships painted in light grey. It can also be used on other issues of similar color such as aircraft or AFVs. Shake well before use. Apply your streak with a fine pointed brush in irregular vertical lines from upper parts on sides and let the paint dry for about 10 minutes. Next take a flat brush moistened in White Spirit and swipe with little pressure over the earlier applied streak to soften the effect and create a natural look.

AK Interactive - Streaking Grime For Light Grey Ships