Airbrush Entire model with AK Interactive Streaking Grime (Enamel Wash) - Well ventilated with a respirator as this stuff is toxic.
Use AK Interactive Rust Streaks (Enamel Wash) for rust streaks where applicable - Well ventilated with a respirator as this stuff is toxic.
Apply weathering powder to base of legs, etc using Vallejo Pigments, Brow Iron Oxide (73.108)