I wanted a method of getting these boys painted quick, but still have them looking decent. With a few tweaks, the method shown by "Elminiaturista" on Instagram worked a treat.

Flames

1. To set the tone, I primed my Brimstone Horrors with German Red Brown .
2. I then pushed the colour brighter with a single coat of Evil Sunz Scarlet .
3. I then washed the whole model with some heavily thinned pure white. I used Liquitex Titanium White ink, but something like Dead White would be just fine too. For the thinner, I mixed in four drops of :contrast medium for every drop of ink.
4. At this point, I painted up the bases. I am going to use the next few steps to give a simple lighting effect around their feet too, streamlining the effect further.
5. The white has settled nicely in the recesses, but I would like it to look extra bright where the light would come from. To give this effect, I gave a quick blast of white ink through my airbrush to the centre of the models. I let the spray hit the area around their feet a little too.
6. I now sprayed the whole mini with Vallejo Yellow Game Ink. I made sure that I covered the areas hit with white on the bases, plus a little extra. If you don't have any yellow ink, I would imagine that a contrast paint like Imperial Fist could work nicely too.
7. Now we pick out al of the raised parts with a drybrush of Evil Sunz Scarlet , bringing back the original colour. Drybrush lightly towards the centre and get heavier the further you get from the source of the light.
8. Now you have a good idea of what the flames will look like ree-stablish the White in deep recesses within large patches of yellow. Make these points of light small for the best effect. To ensure the paint runs into recesses, I used the same 1:4 mix of ink and medium that I used in Step 3.
9. To finish up these minis I added glazes to the most extreme points of the flame. The further I get from the "light source" the darker and less red I got. I dragged my brush away from the centre so more pigment was deposited towards the tip. I started with Evil Sunz Scarlet , then mixed in increasing amounts of Rhinox Hide until it got very brown towards tips. For the very long flames I even mixed in some Abaddon Black , but only applied it to the tips. I finished up by adding dots of pure Abaddon Black to the tips.

Green Eyes

1. First, I painted the eyes and the recesses directly around them with Caliban Green and Abaddon Black . I thinned this paint with a decent amount of water to help flood the recesses.
2. I them painted the eyes themselves with Warpstone Glow .
3. Now, I paint a smaller area with Moot Green .
4. Finally, finish of the eyeball with the tiniest dot of pure white you can. I used Dead White .

Teeth

1. Basecoat the teeth with Ushabti Bone .
2. I then made a with a drop of Skeleton Horde , one of Wyldwood and two drops of Contrast Medium . I went over all of the teeth witha fine brush ensuring I deposited the mix in recesses around them, maximizing contrast.
3. I then repainted the centre of the teeth with thin Ushabti Bone , avoiding recesses. Pull the brushstrokes towards the tips.
4. Then paint a much smaller highlight with Screaming Skull .
5. Finally, finish the teeth with dot highlights of pure white. I used Dead White again.