Airbrush?
Sponge?
Brushes?
Marvy work.
Except the airbrush all of it.
1st removed some flash lines from the kit.
Then serious wash (mixture of black and brown).
The some red-brown rust stains painted on with a brush.
Then some Tamiya weathering powder with a small sponge.
Then some edge highlighting with a brush.
DONE!