Bart,
Thanks for the kind compliments - much appreciated.
In response to your question, I base coated the figure with acrylic "folk art" craft paints (Plaid brand, I think - big spender !

). As for colours, I custom mixed them using Ron Volstad's artwork in the recent Rottman and Volstad book, "Blitzkrieg" (Concord, 2005) as a rough guide.
I think the jacket was a combination of Burnt Umber and Yellow, with a bit of Burnt Sienna, White and Black to make a darkish khaki on the yellowish side (sorry I can't be more specific, I just played around on the palette until it looked "right"). The shorts were a greenish khaki made from mixing Yellow and Black to make an olive green colour, then I added more White to lighten it, and a bit of Burnt Sienna to "brown it" a bit (really scientific, eh ?). I then went ahead and did my oil shading and highlighting using approximately the same colours and combinations of W&N oils, again all mixed "by eye" using Volstad's artwork.
Luckily for us, as you say, the DAK colours varied quite a bit, so the precise colours are not so crucial.
Apologies for the vagueness of the mixes, but I really am this "slap-dash" when it comes to mixing colours - I just play around until it "looks right" according to my references (and you can't go wrong using Volstad's artwork !)
I hope this helped a bit.
Cheers,
Brian