Well I mixed up 1 bag of SS today using FF OF. I adjusted subcool's recipe for 1.5 bags of soil. When I get hold of some happy frog or black gold, I will add another half bag of that to the mix.
For easier mixing, I mixed all the small ingredients, like azomite, humic acid powder etc very thoroughly with a qt of soil and then mixed that with the bone meal, blood meal and worm castings. Otherwise it's hard to mix 3 tsp of powder with 10gal of soil and get an even mix. With this all mixed up thoroughly, I layered it with the potting soil and mixed it up on a piece of scrap plywood, added 1 gal of water since it's bone dry here in the SW and put it in a black plastic trash can to cook in the sun.
I did add 1/2 cup of Mykos mycorrhizae to the mix.
Other than the potting soil, I had little trouble finding the ingredients. Bone meal etc at a nearby nursery. Azomite & humic acid in small quantities from ebay.