Levi,
My technique..... On sharp edges (turrett seams, edges of hatches, fender angles, etc.) I mix a slightly lighter shade of the camo color and drybrush those points where the camo pattern intersects that edge. Over all, I'll do a dust coat of drybrushing, using a cream color, buff, or very light dunkelgelb. This is built up over a succession of coats where the first coat is almost invisible. This allows it to build up and accumulate on the higher points.
The dust color coat is enough to give the impression of sun fade and a dusting of the overall surface of the cehicle. Too much and it will look like you've white washed it.
There has been some work using filters. Where oil paints that are tones of the camo pattern are brushed over the surface of the vehicle to act as a glaze. These are transparent (essentialy a filter like you would use in lighting or on a lens) and do alot to knock down the hard edge or contrast of the camo pattern and are a nice effeect for really giving the impression of a vehicle in the field. Dry brushing can be done over this but lighter than you would use without filters.
Mike
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