Hitman, I guess the secret lies in actually base coloring the model white so the flames are really bright. You paint the black of the skin on top of that.
That's almost is exactly, but I primed it black first, then primed only the cracks/fire white. The steps for painting the fig were:
1) Paint the whole thing black
2) Paint the flames, cracks, mouth, eyes, and everywhere with flames with a white undercoat
3) Note that fire highlighting is reverse to normal: you go from light in the lower parts to dark on the higher parts; basically what happens is the fire/magma cools as it gets away from the body, so it darkens as it cools.
4) Fire highlight scheme: ivory->yellow->light orange->dark orange->red->red brown->black
5) Fix the shape of the cracks; the cracks on the wings actually aren't sculpted on and were basically freehand... It made for a lot of fixing and making smooth edges.
6) And finally, I slacked off an highlighted the wings by drybrushing a couple of successively lighter shades of gray.
Thanks again for all the feedback, appreciated!
n.