I didn’t want to over weather this van as I should imagine these were kept in pretty good condition in the era I am modelling.There is a video Steaming Back to the Sixties part 1 where a Nepean Milk MRC seen briefly is white and in good condition.
To start the process the bogies are removed and the body masked off as I spray a very light coat of self etch black to the roof, chassis and bogies with the wheels in place to enable paint and pastel chalk dust to adhere. Several modellers including Aaron Denning and Ian Millard have held clinics at exhibitions and conventions on how to do this and are expert in weathering loco’s and rolling stock. Next a fine spray of Floquil grime is carefully sprayed to the chassis, roof and bogies. Then the masking tape is removed and work begins on building up the weathering to the sides and ends with soft pastel chalks from a good art supplies, colours do vary to the area of the country that is modelled. Using a flat brush apply a dark grey or black chalk in a vertical motion. If too much is applied remove it carefully with a cotton tip dipped in water and remove the excess by vertical strokes until you are happy, this could take a bit of time so patience is the key here. If there are other colours you wish to use blend them in subtly using the same method. Chalk rust is used around any iron work you wish to rust up a bit With the roof,chassis and bogies I have used a light grey to highlight the detail, after that colours were used that blend in with the scenery unless you want add a bit more . A final spray of thinned dull coat and that should be just about finished.