In order to harmonize the shades of the camo and to subtly vary its hue, I applied some oil color filters on the whole model. Then I used some pin washes to highlight small details.
For the filters I made several attemps, applying each time a new color until I achieved the desired result. In all the cases I used oil colors, diluted at 90-95% with turpentine and applied with a soft large paintbrush. First of all, however, I applied a coat of satin varnish in order to protect the underlying colors and to improve the grip of the filters.
The original shade was, in my opinion, too cold, so I applied a first filter using yellow ochre; the resulting hue was yet too yellowish, so I put on a second filter using cobalt blue and turning the whole color towards green. Finally, thanks to a third and last vermillion red filter I achieved the desired tint.
In the following photos, the picture at the top shows a comparison between the original color and the hue after the application of yellow and blue filters, the bottom one the comparison between the latter one and the application of the red filter.
Generally speaking, I prefer to not apply a general wash with dark colors, because it dims too much the camo tones. I rather use pin (selective) washes, that allow me better control on the final result. The thinning ratio, in this case, is less than in the filters, about 60% of turpentine.
I apply the wash with a fine tip paintbrush, whereas for the smaller details I first wet the surface with pure turpentine, so that it helps the color to flow more easily. After about ten minutes, the time for the thinner to dry, I remove the possible excesses with a clean paintbrush soaked with turpentine.
In the following photo you can see the difference before and after the washes. Notice how the details become more visible and the look itself gains some depth.
I made a first wash using Raw Umber, that has a gentler effect on the lighter hues. I applied it on all the protruding details and between the panel lines, including the zones with anti-slip. In the latter case the color spread by capillarity, resulting incidentally in an interesting color variation.
I eventually retouched the larger details with Van Dyck Brown, darker than the previous color, to further highlight them. This time, however, I didn't touch the anti-slip, where possible spreads would have been too much evident.
Finally I applied a heavier wash with van Dick Brown and Mars Black to the wheels, and a lighter one, with only Mars Black, to the engine grills, in order to give an illusion of depth (although barely visible in the photo).