After finishing chipping I always take photos and review them carefully. It's strange, because just like my artwork, in a photo mistakes instantly jump out of a photo that I don't see when viewing the actual model.
After deciding what my changes will be, I use Photoshop to highlight areas in the photo that need to be changed, adding or removing chipping, oil streaks, rusting, etc. It's then just a question of following my photo guide. These photo sessions are normally repeated many times before I'm happy, thus the reason my builds take so long.
In the photo above you can see the chipping and streaks that represent rust, dust and fuel/oil. I personally like very weathered machines so use my full weathering arsenal.
Above you can see the tracks have been muddied up. I wanted a vehicle that had recently driven through mud, but that also had some dry mud caked into the tracks - the wet and dry mud help to create some extra visual interest. I mixed white glue, pigments and other bits and pieces to thicken up the gooey mess. Later on I added another layer in which I mixed in static grass and pieces found in my garden. To speed up the drying process I used a hair dryer.
I used the same muddy mixture, but watered down, to flick onto the hull. I used a short, stiff- bristled brush dipped it into my mixture, and using my finger flicked the loaded bristles to create the mud spattered effect. A post-it was used to cover areas I wanted to stay clean,
Here's another view of the lower hull that I was still working on.
See the final reveal HERE