If you want useful advice you should post some more information about exactly why your test models aren't looking good. Are you having trouble coming up with a color scheme that you like? Do you have a scheme in mind but can't get it to look right on the test models (and if so, what about them doesn't look right)? Are you having trouble with painting techniques (highlights/shading, etc) in general? When you say you want a "nice matte look" do you mean that your models are too glossy (easily fixed with a coat of matte varnish) or do you mean that you want a dull color scheme? Pictures would be ideal, but anything you can post will help us figure out what advice to give you.
Million wrote:So given that they're very much inspired by WW2 German infantry, take a look at some historical miniature painting forums for step by step guides, and archive pictures of Nazi troops for inspiration
WWI infantry, you mean.
DKoK are a mix of elements from various WWI armies, so that's a good historical starting point.