This was my entry for 40k single mini at UK GD this year. I did most of this one back in June I think - it's a while ago now!
The inspiration came mainly from a piece of artwork in the chaos marine codex (the old codex now I guess!). If you want to check it out, it's on page 63, the 'rise of daemon prince periclitor' or something like that hehe...it's a black and white artwork, it should be pretty obvious which figure I was looking at.
To make the mini, I used a plastic space marine torso and legs to start, then cut the legs at all the joints and re-arranged them in the position I wanted using pins etc.. Then I sculpted the nurgle armour over the top, using the plastic marine as the basic structure. I wanted the nurgle marine to be a lot bulkier and more heavy-looking than normal marines, so it helped to have the plastic one inside, because it meant that it automatically became more chunky. The armour is sculpted with a mix of greenstuff and milliput yellow-grey - the rest is plain greenstuff.
For the painting, a lot of inspiration came from Cyril's nurgle marine from the Ravage Mix Open last year - different shades of green and so on. I wanted to try something more complex and ambitious with the weathering, making the damage more extensive. It was a bit of an experiment - there was a lot of frustration and heartache involved haha, and I wasn't happy with the finished result, but hopefully it looks ok!
It is a little tricky to describe the exact colours I used for the armour, because I did a lot of mixing on the palette, and used a great variety of tones with many glazes and layers. But I will give you an approximation.
The base colour for the green armour was something like GW Camo Green + GW Desert Yellow and perhaps a little GW Fortress Grey if the colour seems a little bright. Then to begin shading, I moved the colour more towards true green: maybe GW Camo Green + a little dark blue (like Regal Blue perhaps) and grey. Then more shading with a dark blue-green colour - add more dark blue to the mix. Then add more dark blue and black, with a touch of red. And finally, very dark purple for the darkest parts - very very dark.
For the highlights, I moved the base colour more towards yellow. So I added more GW Desert Yellow to the Camo Green basecoat mix, then maybe some GW Bleached Bone - maybe with a tiny touch of GW Snakebite Leather. Then more bleached bone and a little white.
Once I had done all this, I also used some 'filters' to modify the colour a little in places. They are like thin glazes using a much stronger colour, to add a little more life and colour nuance to the surface. I used some glazes of P3 necrotite green - a very bright green. And then some more filters with a yellow colour like snakebite leather in places, and more filters with a blue-green colour like hawk turquoise maybe. The turquoise and snakebite leather should overlap in places to create a green-ish tint.
For the chips and damge: I started by trying to use the 'blister pack foam' method, and the masking fluid method, but I was not totally happy and ended up re-working almost all of it just by hand, with a brush haha. But that was a nightmare! So I would still recommend that you try the masking fluid method though, if you want to create something similar - maybe you can then combine it with some smaller chips, using the blister foam dipped in paint. Remember, it is important to apply the masking fluid it before you begin to paint the green armour, and it will require you to paint the armour in another colour first - a dark brown colour for the chips to show through.
The chips colour: A good colour to use is a dark brown - something like scorched brown with black. Although actually, it might create a better contrast if it is a slightly more saturated brown, so why don't you try dark flesh mixed with black. Within the larger chips, you can add some extra colour and texture. Look at some rust in real life to get ideas for the colours. You can use a variety of stronger orange and red browns, and some more sudbued red-browns for older rust. You can add texture by dabbing on some pigments carefully.