Thanks guys.
As far as my workflow I only use Substance Painter materials and a variety of Smart Materials and Smart Masks. These help me get more specific types of weathering such as edge wear, dust, sand in crevices, etc..
It is a lot of material layers, with a black mask added and painting/generating white onto the masks. For example, I would add one of either 'Mortar Wall' or 'Leather Rough' materials that look like dirt, then turn it darkish or brown in color. Then I'd drag and drop different smart masks, removing them and trying other ones until I find a suitable one. I may make a video showing a top-to-bottom texturing of one of the brakevans later.