Trouble with flames

I’m trying to make some realisic flames go around my band’s logo but I’m having some issue with doing it. I found a nice tutorial by deathpen here:

It is a good start, and I’ve messed aorund with the shape tweening quite a bit, but I cannot figure out how to make the shape tween work correctly. When I shape tween my flame, the shapes I draw will sort of disappear and reappear so when I look at it even with the glow and blur filters it just looks like blobs moving around on the stage. Are there any good tutorials on how to make realistic flames in flash?

Thanks in advance.