@ Phil: I used those acrylics you can buy at arts and crafts stores, it comes in large squeeze bottles, and very thick, but when mixed to the right consistancy they airbrush very nicely, and are very forgiving. I made the mud with MMP powder medium earth mixed int an oil wash. and applied it with a brush.
@NIcoropi: I used mineral spirits, not turpentine. I've never tried turpentine, and I have had good results with the spriits.
@Prato: I tried replicating what I saw on my R/C stuart after I had driven it through the mud. Mud built up on the hull where the tracks had rubbed against it, built up on the uppersides of everything, it also built up heavily on the road wheels,drive sprocket, and idler, but didn't really dirty up the inside of the tracks too much. the inside of the tracks. I tried replicating what happens when you drive through relatively watery mud, so it didn't really get up on the fenders too much.
Lord Dave
You know you're a modeler when....
a:your fingers are forever encrusted with dried paint/cured glue
b:you smell of enamel thinner, glue, and paint 24/7
c:you shed a tear when the hobby shop closes.
piggy # 76 Lord Stomp and Mig hater