I've pretty much just been making it up as I go. I had seen ScareFX's how-to last year and was determined to build my own witch this year. I didn't consult ScareFX's how-to again until I had my first frame already built. After seeing how ScareFX's witch leaned forward, I decided I wanted to have a simliar "lean", so I reconstructed the entire upper frame. I like to call this the "iterative" approach.
I have some small pictures of the frame up on http://www.hauntsoft.com
. I will do a more complete how-to with better pictures later on, but probably not until after Halloween.
Edit: Opps... forgot to answer your question about whether or not I'm chilling the fog. I'm not. I'd rather have the fog rise up similiar to steam and smoke. I'd be worried about the fog never coming out of the cauldron if it were chilled. Not sure if others have tried it, so I could be wrong.