Airbrush on the Dark Orange Rust Colour first as a base, then go over in a mottling fashion with Light Orange Rust to create a tonal difference. Then with a paint brush, brush on some random splotches using a dark blue colour such as SMS PL71 Insignia Blue and then around the edges of that with Red Rust, Red Oxide or a dark brown colour of your choice.

Then tie it together with a very light dusting coat of Red Rust or Red Oxide through the air brush and finish up by dry brushing on a mix of SMS Weathering Pigments Earth & Red Earth.
 

Experiment and find out the best way that works for you!

SET CONTAINS 4 COLOURS : 
 

• Light Orange Rust 30ml
• Dark Orange Rust 30ml
• Red Rust 30ml
• Red Oxide 30ml