Cardboard works so much easier than plastic. Just bending without heating it
Sanding the basic shape is just a minutes work. And after the quick and easy build fixate is all with the resin. Well basecally the same way Formula 1 cars are build. I just use cardboard instead of carbon. And my resin doesn't need to go into an autoclave ;-)
The crashed cab just got some rust

The salt technique doesn't work without the airbrush. Luckely rust comes in more shapes than one