you can try a volumetric lighting set-up with textures. you can get this tute in the newtek website under special effects. Word of caution though, it took me 5 full hours to render a 60 frame clip!
when I use flame effects, I mostly use adobe after effects. some masking, image maps and loads of filtering and the staple feathering. it takes considerably less time to render and you will be able to manipulate it better in terms of its interaction with other elements in the scene.
but its up to you.
asha_hardwire