Because of how the glow is flowing around the stones, this is more of a lava effect. But if you're looking to paint fire or similar glow effects, this should still work.
If you want to get fancier with your fire, stick around for the 3rd and final Pyre Troll WIP later this week.
So to start, I gave the whole body a stone-like sponging which you can see in the first post.
The first step is to put down a base coat of white that the brighter colours can be painted on top of. That's the down side of the strong yellows, greens, reds or neons. Not always necessary, but a white base coat will bring the most out of your colours. For a stronger white, I actually used gesso.
If you were just painting lava, it'd be easy to know where to paint the white - just use the natural cracks or around stones. As a beast, I had to trace the contours of his body, not just the stony ridges. This meant emphasizing muscles as well.
For the base colour coat, I used a neon yellow paint. (Found from a generic hobby / paint store - Michaels or Hobby Lobby for example) Neon's just stronger, but a regular yellow will work too. Nothing wrong here with overlapping on the stone a little.
Next up are the green layers. At first I tried neon green.. but found that a darker green created the effect best. I paint the green over both the yellow and the stone, more so the stone, but if the "lava flow" was wider, I'd probably balance it out differently.
You can click the next pic to see it bigger, but I've done a few layers of paint here. Not just green, but green with different mixes of grey to blend and create the glow effect. Also worth noting, is when you blend a lighter colour like green over a darker one like grey / black, you'll end up with a little "natural" blend as the darker colours show through the lighter paint.
Glows aren't just about colour mind you. Here I've stepped back down to white - focusing on joints and a little randomness. The white actually appears to brighten the glow.
After a little bit of matte varnish, here's a detail close-up of the Pyre Troll's back.
 | Take a look at my Step by Step page for the entire Hordebloods project. Here you will find each model broken down into links showing each step: Concept, Works in Progress, (for both modelling and painting) and Final Shots |