Hey, thanks all!
Roosterpelo, I've been following the progress on your sherm in the armor forum. By the way, do you know if you can repost or copy a thread in another forum?
The mud is Celluclay. Well, actually its called Sculptamold but I think its the same thing. It is a cellulose powder used for making groundwork in dios. I mixed it with water and black and brown paint. Then I used a paint brush(or a screwdriver, popsicle stick, etc.) to spread it around with. I put it on pretty thick on the hull and suspension where the mud would accumulate. Then I used a brush and just put a little on the sides for "spatter." Once you put it on, you can wipe most of it off for kind of a film of thin mud. After it was dried, I drybrushed it with lighter and lighter shades of brown/tan because the higher points dry faster. For dry mud, you could also just make the "battter" a lighter tan or gray to start with. Also youd probably want a little mud on the decks/turret from where the crew climbs in with muddy feet. This is just how I did it, you could probably experiment with it all kinds of ways to find how it works best for you.
Hope that helps, I probably made it sound more complicated than it really is.
Thanks again for your comments everybody!
--------------------------------------------------------------------------------Kevin