best way to add grit to the tracks and tires

[1crazygamer]

Secret Weapon's weathering pigments are very nice.

[Spartiatis]

Are ground pastels the same as using pigments?

[Kamui]

I haven't tried the pigments yet but I've seen plenty of photos to suggest they are great.

In the spaces where a bit more will stick I use a very light application of fine sand. Not an even coating just some scattered grains to suggest texture. Then I paint the area a muddy color, and drybrush the same color across the areas that would get dirty but wouldn't see much buildup. You can also add flock and/or static grass in small amounts and paint over it to represent large chunks of sod and turf. This can be a nice effect for dozer blades or steps where there is a surface to catch debris but not so good on the sides where such chunks are going to slide off quickly.