Geistware: I've tried using sawdust and CA and found it really nasty to sand- it's like rock. Maybe this method would be used for gaps on internal joints? Not that I'm a pro or anything, but I've really screwed a fuse I'm fixing using that method. What application do you use it for?

But I've never used Micoballoons....being so new at this.

DS: as I'm mentioning in this post, sawdust and ca gets really hard. I know that epoxy gets hard like that too. Does Microballoons make the epoxy easier to sand to shape?