Lets talk about how it dries, its wet and dark and as it dries up it becomes lighter and thinner like sand. It also piles up on its self with the newest wettest mud on top of old dry mud (light to dark).
I have used lots of products over the years and there are many to choose from. I really like doing mud in three shades, Light-Medium-Dark to do this I will use Tamiya Diorama Texture Paint (Light and Dark) and I will use Wet Ground by AK Interactive for the final wet mud.
Untitled by jon newsom, on FlickrLots of Tracks
Untitled by jon newsom, on FlickrThis stuff is approx $25 a bottle so we need to water it down in a cup where its mixed and then applied.
Untitled by jon newsom, on FlickrNext we mix some that is not diluted with water for the tank, Im using mostly the light with a little dark mixed in.
Untitled by jon newsom, on FlickrIts so light its hardly noticeable and thats exactly what you want!
Untitled by jon newsom, on Flickrmake sure to get it in all the right places, as the track turns forward mud is slung up on the rear of the armor plates more than the front and lots in between.
Untitled by jon newsom, on FlickrNext is the mid tones which cover the light but not all the way, I basically dry-brush it on making sure not to cover all the light.
Untitled by jon newsom, on FlickrA boot stamp is always fun to add a few muddy boot prints to the engine deck or other places.
Untitled by jon newsom, on FlickrNext I cut up some Woodland Scenics field grass and flock grass and an assortment of tiny sticks and organic debris.
Untitled by jon newsom, on FlickrMix it well once added to my AK mud to give it an authentic texture.
Untitled by jon newsom, on FlickrOnce mixed it it added to the top of the mid-tone but again I make sure I leave mid and light tones visible.
Untitled by jon newsom, on FlickrAdd it to the tracks and the wheels, on the Henglong do a small section at a time then let it dry for 10 min and then move track around to ensure it is still flexible for RC use later.
Untitled by jon newsom, on FlickrAlso for RC use it must be hardened with a heatgun, this way it will survive the elements later and wont break or shatter from impacts. just be sure the gun is on low and you take your time and keep your distance. You dont want to effect the plastic below.
Untitled by jon newsom, on FlickrThe final result is undeniable and will catch your eye from across the room.
Untitled by jon newsom, on FlickrA few more odds and ends and these two Tigers will be ready for their final pictures!
I definitely see TOTM in the near future! 
