This is my first attempt at modelling a knocked out vehicle, so please be gentle with the criticism! And no, it isnt kit-bashed from an intact vehicle, its the resin "Wrecked Hanomag" kit from Warlord built straight out of the box.
I used a combination of airbrushed rust base colours around the damaged areas, and then a series of pigments over that to deepen the effect. It wasnt a project where I ever felt fully in control of the final result... I just had to keep experimenting until I got to a point where I felt it "good enough".