After a considerable break - I decided to give weathering another shot. I followed the tutorial that Piers wrote on the Guild and began by adding Weathering Fixer to the model with a brush.
Once that was done, I added MIG earth pigment with an old brush. Stippling around the edge of the tank and the paying particularly attention to the tracks and rear.
When I added the pigment, it looked very odd, like I'd splashed paint on the model. However, once it dried and I brushed the excess off with an old makeup brush of Mrs. Kinch's. A considerable amount of the pigment came off and what was there was spread out a lot more. I think I'll have to make sure I do this step on a piece of white paper as it struck me that I was wasting quite a bit of pigment that could be reused.