various layers with orange and yellow and white bits, smudged appropriately into flame shapes. then a layer over the lineart set to 'hard light' and do basically the same... work at until you're happy.
I think Torch came out pretty cool. Fire has always been a tough effect for me to do. The only thing that's getting me is Ben. I know it's tough because of the texture but his face doesn't seem to have any specific light source. Personally I think I would have added a lightsource coming from that bottom right corner. I know you've got that on Sue and Reed buy the Thing seems to be missing it.
But that's just me. I'm a sucker for secondary light sources.