Oops...I forgot to mention that for the stuff not listed in percentages (i.e. the ferts), the listed amount is (roughly) per gallon of soil mix. I'll edit the post above to reflect that...
Also, as 3H mentions, this is not an exact science...when in doubt use a little less, not a little more.
So if you have 5 3-gallon pots, you would be making 15 gallons of soil mix, so you would add (roughly) 15 T each of blood and bone meal, 25-30 T of kelp meal, and 30-60 T of rock phosphate.
Also, for ease of measuring:
16 T = 1 cup
12 T = 3/4 cup
8 T = 1/2 cup
4 T = 1/4 cup
Sorry for the earlier confusion.
O