One of the big questions anyone who tries to paint Great War Germans eventually faces is that of deciding exactly what constitutes "feldgrau". I have to admit that I've found the question particularly troublesome, and the source of not a little painter's angst. Below you'll see a variety of primary illustrative sources, mostly gleaned from web searches.
Early War feldgrau, at least from these images, seems to lie closer to the green end of the color spectrum. This is also evinced from the excellent original uniforms found in Laurent Mirouze's World War I Infantry in Colour Photographs. I'm leaving aside here the vexing but valid question regarding the fading or discoloration of century-old images and artifacts.
Delving into sources like Osprey and Mollo produces a bewildering variety of interpretations, as is shown below, many clearly more grey than green:
In the end, I found a combination of colors, shading, and washes that at least satisfied my desire to create a distinction between these early war uniforms and those of later years represented in my collection.
I undercoated the figures with a black Krylon primer, which gave them a slight sheen. This is not quite semi-gloss, but helps in a number of ways. Firstly, it seems to make the details stand out and easier for me to distinguish given my deteriorating middle-age eyesight. Secondly, the very subtle semi-gloss undercoat helps with the flow of washes in a way that doesn't work for me with a purely matt undercoat. For faces I used the following built up layers:
1) Foundry Flesh Shade 5a; 2) Games Workshop Elf Flesh 61.23; 3) Vallejo Basic Skin Tone 815; 4) Vallejo Salmon Rose 835.
I don't worry about painting the eyes unless they are really well sculpted. I've found their realistic rendition one of the greatest challenges in painting. Get it wrong and you mess up what would be an otherwise presentable paint job.
There are many different ways to create the look of skin. I've experimented with a variety of possible combinations, and this is the one that causes me the least grief at the moment.
For the uniform, I used the following:
1) base coat with Vallejo German Fieldgrey WW2 830; 2) highlight with Vallejo Green Grey 886; 3) Leather boots and belts: Vallejo Red Leather 818; 4) highlight leather with Vallejo Orange Brown 981.
The penultimate step is to wash the figure, apart from the face, and any white parts, with Asphaltum (I'll explain how I produce this in my next blog post). This acts something like a filter, and tends to blend the transitions between previous layers, and also provides a sense of depth to the deepest recesses.
Lastly, once things have dried, go over the miniature with your second highlight - in this case Green Grey and Orange Brown.