Actually I have seen your smoke trail tutorial and I thought it was excellent.  I had  considered using that method but just didn't have time.  I would have to create the splat which probably isn't too hard but not easy either (nothing is easy the first time!).

The other thing I was thinking of was just to use a regulat particle generator with spheres and play with the variation in sizes.  There are still options to explore.

I'm bummed that the volumetric clouds don't work when they're small (only when they're big).  Kind of weird.  I don't know how they're coded to work but I'm quite curious now.

The biggest part of smoke/clouds that makes it really hard is that dang subsurface scattering effect.  Volumetrics are nice and it's something C could use.  For some reason, I thought Bryce has volumetric textures but I'm not sure.

-Kix