This batch of wagons are very different and the approach to weathering is also diverse.
Firstly the dear old 16T Mineral wagon – I have weathered many tens of these wagons and most have been grey – this one is of the brown, fitted example. Matt Black is the base wash and wipe colour and three tones of rust were used.
The next wagon is a Catfish Ballast Wagon, the wash and wipe on this wagon was a light grey. The inside of the hopper also had a little light rust added before being filled with O Gauge Ballast. The Ballast is left for an hour and then emptied out to give the desired effect. I look on this method as only reproducing what happens in the real world!
Lastly we have an OAA Open Wagon in Bauxite. After adding the door chains to the sides, these were painted medium rust. I then used a very dark brown to do the wash and wipe with.
Finally the photo below shows the diverse wash and wipe used.