Yes, but I'm still having problems. There seems to be some inconsistency when rendering; one time background is transparent, but ground turns black, second time it turns white. I had it working once, but in a second render it was wrong again. Very weird. And also when using 2 cards (fire and smoke), it's not always going well.
Okay, painting in is easier, but I'd still like to know why. And it may be something that needs debugging.
So here's a few files (you have to recall png's) and a test I did.
Anyone has a better solution, please post.