The way I test the vermic/perlite mixture is to squeeze it like Heather says and make sure no water drips out and it condenses like that but when you poke it, it immediately collapses. That seems to be the just right amount of moisture. You'll get a real workout mixing the dry mix then adding the water. You need to mix and mix and if you think you're done, mix some more LOL. I think that step can't be overstated since you want the water you add completely and evenly incorporated into the dry mixture.
Just to add to your excellent write up Heather here's a couple of pictures of clutches set up in a vermiculite/perlite mixture like yours.....
