Yeah, I did the latter. Mix it up and then let it sit in a plastic bin for a month or so. You should be able to find everything you need a home depot or lowes.
The soil base is simple:
5 parts Canadian Sphagnum Peat or Coir or Pro-Moss
3 parts perlite
2 parts worm castings or mushroom compost or home made compost
Powdered (NOT PELLETED) dolomite lime @ 2 tablespoons per gallon or 1 cup per cubic foot of the soiless mix.
Take some of this and set it aside for seedlings or freshly rooted clones.
To the rest ammend to each gallon of soil mix:
1 tablespoon Blood meal
2 tablespoons Bone meal
1-tablespoon Kelp meal
(OPTIONAL) 1 tablespoon Jersey Greensand
This came from an extremely long thread on ICMag.
https://www.icmag.com/ic/showthread.php?threadid=53792
Here is a post where I mixed it up.