to create your own flames, use a brush shaped like a thin bar, slightly thicker on the ends. Then have that brush rotate as you paint in fairly directional paths. Use a blend or transfer function that builds up like screen or multiply and use a fairly low transparency or flowrate. As the brush rotates the edges build up and give you that cool intenside edge and gossamer middle.
There is also a package called Flame out there (free even) that will generate whispy’s for you.