I know of this stuff only because i have done some construction work.
It is an expanding insulative foam. That's it.
If you are going to use it in molds you HAVE to add a silicone type product to the mold otherwise it will stick to it and destroy the mold. While expensive, you can use a product called "Aromor All' for cars. Make sure you get the kind with silicone in it. It is a vnyl cleaner and protector. It might be called something different where you are. Get it Canadian tire or an automotive store.
Spray the mold thoroughly. Almost thickly. After it dries you add the mountain in minutes or insulative foam into the mold.
If it is slow acting [you can get different kinds] you cn use a bru***o push it gently into the crevices.
It will take about 3 tries before you can start to give a good guessimate of how much you need.
If you go to a home depot [or other large building supply place] you may be able to get a good deal on insulative expanding foam.
It is the same thing.
Just remember to spray on the mold release, the silicone each time.
You will only forget once LOL
And DON'T worry about putting in too much. It may make a mess but it won't destroy your house. LOL
Also do it over newspaper or such.
I hope that helps you guys out.
My name is Stephen and I want to give back to this great hobby.
So please pop over to my website and enjoy the free tutorials.
If you live near me maybe we can share layouts. :)
Have fun and God bless.