I sent you the tgd; there are 2 cloud layers in there, the upper one having a different color adjust so you can sharpen the 'ball'. It's a matter of playing with these balls, so to speak, to get a sharp inner one and a vague outer one, both can have their shininess adjusted.
Lights won't work as nice, as you have to set AA quite high to get rid of the embers. I tried it, and the balls are more subtle. But if you need embers, that works as well, but you need to place all lights by hand.