Most of the early kit that the Afrika Korps took with them was still in dark panzer grey and overpainted on arrival. Often using Italian paint stocks, but sometimes a sand paste mixed with water or petrol. Could be an interesting finish to replicate as that would be more prone to wearing.
Can't remember the dates, but within a few months kit started to arrive from the factory in dessert cammouflage paint. This wouldn't wear down to grey as there was no grey underneath. The Tank Museum at Bovington recently did a video on YouTube about repainting their Tiger in correct DAK colours which was quite revealing about the high quality of the paint used.

Nigel,

The DAK yellow paint really mostly faded away to wind and sun than chipping. Chipping would happen in areas that gotten banged around. To get the effect of the DAK paint showing the grey I first painted the whole tank grey, put down a clear coat and repainted the tank with MIG washable DAK yellow. Waited an hour than using a bush and water removed the yellow paint enough to show the grey to effect of how much wear I wanted it to represent.

Mark

I specialise in small-scale armour (mainly 1/72 and 1/76). How effective this will be on 1/35-scale vehicles I'm not sure, but I tend to use a reverse technique when replicating worn and chipped paintwork (particularly on DAK subjects). I also use enamels rather than acrylics. Essentially, this involves applying a suitable desert colour, and then carefully dry-brushing a dark grey over relevant areas to give the impression of the original paintwork exposed due to sand erosion. Once satisfied with the appearance, I then apply a series of washes, and finally chalk pastel powder to create an overall covering of dust. Rust can also be replicated using chalk pastels, either applied dry, or mixed with a small amount of water. Since my completed models are always incorporated in diorama or vignette settings, there is no risk of them being handled (and the chalk being rubbed off). Consequently, I avoid sealing them with varnish, as this tends to take away the all-important dry dusty appearance.