Best way to add those microbes is with a compost tea, here is a tried and tested recipe from Microbeman from microbeorganics.
Through a plethora of trial and error brewing with a dissolved oxygen meter at hand we determined that a pretty reliable volume of [vermi]compost to use is 2.38% by volume of water used up to around a 250 gallon brewer.
So if you have 5 gallons you multiply that by 2.38% to get the amount of [vermi]compost to use. Then you can go to;
Online Conversion - Volume Conversion and convert it into any unit of measure which is convenient. In my opinion measuring [vermi]compost by weight is inaccurate because of varying moisture content.
Anyway to proceed we have;
5 x 2.38% = 0.119 of a gallon = 0.476 of a quart = 0.450 of a liter
= 450.5 milliliters [450 rounded] = 1.904 cups [2 cups rounded] - Your choice
Likewise with the use of black strap molasses, a percentage of 0.50% is a good median amount to use.
These two ingredients, perhaps surprisingly, comprise the total of inputs in most of our brews these days. This simple recipe, if using an efficient ACT maker and good quality [vermi]compost results in a microbial population made up of the important three groups. This is the only recipe used to date, in all the videos on my Youtube channel ‘Microbe Organics’
To get these three groups the ACT maker should be run for 36 to 42 hours. The ideal temperature range is 65 to 72 Fahrenheit (18 to 22 Celsius), however a little cooler or warmer is okay. I’ve had pretty equivalent results with ambient temperatures around 100 F (38 C) and as cool as 50 F (10 C).
To spill a small secret, [which I hope will not preclude you purchasing the related downloadable video on my webpage in the upcoming future, once I figure how to do it
] I’ve been pre-feeding or pre-activating [vermi]compost which is not so fresh by mixing in a small amount of wheat bran (livestock store or bulk foods department grocery store) and moistening with very diluted black strap molasses, loosely covered with cloth or paper towel 24 hours ahead of brew. (approximate ratios, wheat bran 1:30 [vermi]compost & BSM 1:300 water).
This has, so far resulted in attaining the desired microbial population at 24 hours brew time rather than the usual 36 to 42 hours.