I had used the dye before, but like you said the fizz-just kept F**** up my cast. The fizz would cure on my cast, and removing it is a bi***. If you notice, the RIT Dye is almost the same stuff, but cheaper and no fizz. So far all the times I have used it, it has been great.
And yes the castn'craft is the clear resin in a can. The catalyst is in a little plastic bottle.
And no I don't use a respirator, there is no brain dama-jabba-jaba-gabge.

I work with it outside, and leave it there for curing purposes.
And just an update. I demolded the cast. The matrix came out perfect, I am painting that today. One half of the revolver joint with the locking mechanism got an air bubble that I didn't see, so I have to recast that. The other half with the ratchet side came out good. Just gotta clean it up, and wait to recast the other half.