Not wholly satisfied, as I did not get the look and mood I was after perfectly right.
Here he is, and again, this is not at all a masterpiece, but one of a grunt in an army.
At the base, I did not want a nurgle mutant, so no "diseased" look. I did a clean-ish skin tone relatively close to pink, mostly to inspire... well, "pity" is too strong a word, but you might get my point. This is a poor guy who have been horribly mutated, not a blood thirsty mutant from the wasteland... Then, to honor the ork origin of this mini, I chose a green to dress it up. As a bonus, green complement red on the colour wheel, so it is a good companion to the pinkish skin. Then, I chose my favourite orangy brown for leather, and would use the same colour for the rust of metal parts, thus tying up two parts of the mini. The blue simply came as a complement of the orange. I intend to keep the skin, the green, and the rusty-brown constant through the army, but I will vary the remaining colour so that they don't seem like they wear uniforms.
The result was pretty clean, in the sense of "not dirty looking". So I tried to muck it up... and this is what I think I could have done better... I am not sure the stains and dirt are believable. The figure certainly look stained and dirty, but it's the paint job that look dirty and stained, not the mutant!
I tried to use differently coloured washes to stain the mini, as well as a drybrush of the beige brown I will use on the base... I am open to suggestions as to what went wrong with the staining...
On the sculpting side, tough, i'm quite pleased. It's hard to tell now what is grey plastic and what is green-stuff, so I consider that a success, at least in the green-stuff mastering sense.