thank you friends!
For the method, it is simple. (hope that everybody understand, i use google translator !)
As a reminder, I only painted the acrylic, Liquitex diluted alcohol at 70 ° all passed the single-action airbrush to 10 euros on a well known auction site.
1 / I first had a layer of black on the body
2 / I spend a veil (very diluted paint, very liquid) brown (Raw Umber) once the black dry
3 / I balance of keys Burnt Sienna Burnt in places.
4 / I start my keys with color again a veil of Earth sienna
5 / Once this is done and dry, I spray a good dose of hairspray on the whole and before drying I sprinkle salt.
6 / When the airspray dry, i paint with the last color, here green.
7 / Once the color box is dry, I can only pass the model under water to remove salt and "work" the paint to get the desired effect. In fact the hair spray protects the color of rust base and allows me to remove the green where I want.
8 / Finally, I will complete the effect with touches of rust pigments that will slightly melt the rust stains with paint.
Here, as usual, is my method of pretending, that is relatively simple and efficient!
My tubes for different layers and veils basis for rust: