\ said:
hey, its going to be fairly soft ground i guess because its a desert scene so its mostly sand
Spread some polyfilla where you want the tracks. Place a piece of track in the stuff then move it along. For the Humvee use a pencil or similar and drag this along.
When dry paint the ruts a darker sand than the rest.
Spread a thin coat of P.V.A. over the dio. NOT the ruts.
Get some of yak face's budgie grit and sprinkle it on.
When dry upend the dio. and shake. The grit will stick to the desert area but not the ruts giving an impression of compacted sand. Re-touch with paint if req.
If you care to have a look, I have used this method in my gallery photo 'Snow tiger' minus the sand!!!! but the principle is still the same.
I hope this is of some use and I look forward to some pickies.
Ron