Create either:
*Create a curve, and rebuild it so it has lots of evenly spaced cv's.
Then make that curve an emitter for the fire preset effect.
or
* Create, and animate your curve. (does not need to have lots of cv's)
Then apply a PaintFX brush to it, and tweak the brush
Good luck!
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com