Dust and dry mud applied using tamiya acr. flat earth mixed with buff and red brown thinned (1 to 7-8) with distilled water. Using tamiya paints with water is not a good idea usually however this is a different situation where applying the heavily thinned paint in mists and drying it with the airbrushing to build the layers slowly and panel by panel is required. Also it’s relatively error proof for it can be easily removed with a damp brush and since the basecoat is thinned with proper thinners and the weathering on top of it is all oil paints, this technique is harmless to the underlying layers!
What’s left now is pigments for rust, fresh mud and various other stains etc. Eventho the dust layer was with all flat paints, it didnt tone the semi gloss sheen as much as i’ve expected it to, so it looks like in the end it’s gonna receive a matt coat – which is usually a frightening affair for me due to risk of matt coat frosting on the model!