The basic PF recipe is 1/4 cup brown rice flour (measure the flour itself, not the brown rice if you grind it yourself), 1/2 cup vermiculite(fine is prefered), and 60ml (4 tablespoons) of water per jar.
For 5 jars, you use the 2:1:1 recipe. Thats 2 cups of verm, 1 cup water, and 1 cup of brown rice flour. 1 cup is 240ml.
Depending on the vermiculite used, the amount of water needed can vary. To prevent a overly dry or wet mixture you can prepare the substrate this way:
Put the required amount of vermiculite in a bowl (all at once, NOT for each jar separately!). Use a spatula or spoon to mix in enough water to saturate the vermiculite to the field capacity, mix well.
The field capacity is reached when a small puddle,barely visible, forms at the bottom of the bowl when you tilt it. Then add the appropriate amount of BRF and mix together.(This works best if you use 1/2 cup vermiculite and 1/6 cup BRF per 1/2 pint jar)
The idea is to coat the wet vermiculite particles with the dry powder as you stir the mix with the spatula.