You'll get your wish my friend... I'll do just that. I'm ready to start "mudding" on a couple vehicles right now...
Here's the start point of a Panzer IV:
I've started using a worn-out 1/4" flat brush that I trimmed down to about 1/4" in bristle-length. I dip the brush in the sheetrock mud and apply it to the sides of the hull and undersides of the fenders with a stippling/stabbing motion, and keep stabbing it all around... Very similar to texturing sheetrock, lol..
Moving onto the underside. I applied a bit of mud with my finger.
Then I touch and lift my finger repeatedly to texture the mud..
I let that dry, then add more, repeating the process until I get the effect and thickness I want.. Then it's paint the mud with a good "mud color" (I use tempera paint for this) that I mix up, keeping in mind that it has to match the local terrain color. For instance, if I was doing the Vietnam Central Highlands or even Ft Benning or Ft Sill, I'd be using a color that's visibly reddish brown to simulate those area's red clay... Once that's done. then drybrush with a lighter shade for dry mud... If the mud is still wet, a use a clear satin finish over it to give it some "moisture". I think gloss is TOO wet-looking, personally..
Here's the stuff on my Luchs:
Hope this gives you some ideas..
For dust, an airbrush works well for nice even, recent coat, but that's about it.. Dust accumulates in the lower areas, in the craks and crevasses, and against ridges and in corners.. It also gets on things in heavier concentrations towards the rear of armored vehicles, and is heavy at the bottom, then get proggressively lighter as you go higher on the vehicle. It doesn't stay on areas that get exposed to the wind while moving generally, but in some instances, it gets EVERYWHERE... Like in the desert, the dust is a real choker, billowing up in clouds that can seen from miles away, especially if a column is generating it.. The same holds true for the dust on tank trails on stateside posts.. Ft Hood, for example.. The dirt on the tank trails there in the summer gets ground to the conistancy of flour and is about an inch or two deep... Somedays, it looked like our tracks were painted tan and you didn't know they were green until it rained, lol..
But overall, the best way, in my opinion, is to use pastels for dust, since it's dust.. Tap it onto the model from a wide soft brush, then move it around into the corners, low spots, and such..