Here is a 28mm scale truck, the first vehicle I've painted in this scale. I started with a base layer of tan, then used a variety of technical paints to cover the truck with mud, dust, and grime. I think I went too far, though; I wanted more of a weathering effect, as opposed to having the truck look like it's just returned from off-roading. I think part of my mistake was starting with a base colour that was too close to the filth I slathered atop it, too.
I have two more vehicles in this scale. I'm going to paint those army green, and then try my hand at more subtle weathering effects.