ASTRA MILITARUM, Imperial Guard Colour Scheme

I'm currently figuring out how to paint my imperial guard and would really appreciate some advice.

I want the troups to look like these guys.

https://pin.it/myup2fdmqohcwv

https://pin.it/hkgnq4tzjjzxs3

It's like this horribly beautiful intense brown-green.

Here's progress so far.

I think I'm slowly getting there. Although it is a faff to do because it involves lots of mixing paint.

Basecoat = Airbrush with 3:2 Vallejo camo green:GW steel legion brown
Highlight = Airbrush with 3:2 Vallejo camo green:GW zandri dust
Shade = Airbrush with 1:1:1 Vallejo camo green:GW castellan green:GW

https://www.warhammer-community.com/2016/11/13/citadel-paints/
http://www.abload.de/img/citadelnewpaintrangewpu6p.jpg
I can't really find anything here that gives a similar sort of brown-green, any ideas? Ideally, I'd prefer a vallejo colour given the dropper bottles and that they don't change their paint line every other year...

Instead, I've tried to use the brown ink as a glaze to introduce more of the brown colour from the concept images.

Left figure - no washes
Middle figure - one glaze GW brown ink (old) 1:1 with Vallejo glaze medium, one wash GW nuln oil
RIght figure - two glazes GW brown ink (old) 1:1 with Vallejo glaze medium, one wash GW nuln oil

I have to say I'm very impressed with the nuln oil wash

I prefer the colour on the middle figure the most, but the highlights and low lights still aren't 'popping' like they do in this image. The double glaze just looks a bit messy and too dark.

So I think i need to put an extra highlight and shade in there before I do the wash. I think it's because I did zenithal highlights with an airbrush which flattens the top when viewed from above.

I was thinking edge highlight = 3:2 Vallejo camo green:GW Screaming skull
And I might just use diluted black for the darkest shadows on the shade as it's already pretty dark.
THEN doing the washes, but this might dampen the highlights too much and I don't know if I'll be able to re do them because of the colour shift caused by the glaze...

But, I'd LOVE a simpler option if any one has any ideas.

~M