The finished vehicle can be seen to have a very light weathering, road dirt accumulated from a short time in service (possibly since its last heavy overhaul) and nothing allowed to become totally obscured by grime. Windows are still relatively clean and only edges and corners have accumulated dirt so far. There is a slightly heavier accumulation in crooks and nannies and on the underframe but, for the most part, it is a good advertisement for the company.
Materials and tools used were minimal, but the time taken wasn't. Placing weathering materials carefully rather than just sloshing them on can take up a lot of time, especially if once it's on you can't remove it entirely!
The finished product looks like this: