I never bought into that. Get a five gallon bucket and a couple of dry cow pies. Stir daily until there is no odor.Drain/strain and mix 50/50 with water.Dunk your plants in it for a minute or so.
I make mine in a 55 gallon drum. I use it on everything.
The cheapest 20-20-20 you can get is fine as a foliar spray, although not really necessary.In the orchid world it's all about roots.
Bromeliads are the epiphytics that need foliar ( in the center of the cup).
Actually, I completely agree. I only use the formula(s) I described for repotting and/or establishing plants with few or compromised root systems.
For my normal fertilizing, I use only compost extract diluted in water. As you noted, it's free and in my experience works at least as well as anything else.
Here's a good article about such things... Biostimulating turfgrasses