AMMO by MIG Weathering Effects. - Acrylic Effects for Modelling
Item: Scratches Effects

From the Manufacturer:

A revolutionary product to be used for creating scratches and surface wear. Apply a base layer of acrylic paint, a layer of Scratches Effect followed by a top layer of acrylic paint. When dry, moisten area with water and the gently scrub using a stiff brush and watch small scratches and wear appear on the surface.