Yeah that stuff is great for foliar feeding. This year I've only been using Alaska Fish Emulations (5-1-1) during my plant's vegetative phase and I haven't had any deficiency problems. I mix 1-2 tablespoons in a gallon of water, I pour most of it on the soil, but save a little for my spray bottle. It smells horrible and you want to make a fresh batch every time, but otherwise it's really good stuff. Another fish fertilizer to look into is Fish Hydrolysate. It's basically the same stuff, but processed a little different, and has more nutrients.
You are so right about the foliar feeding, seems that it has become such a lost art among the younger growers, our plants and gardens. There are so many benefits which can obtained by foliar feeding and it is such an economical way to add many different products. When a deficiency does show up it usually can be handled with a spray of something or another and not upset your entire soil mixture or structure.
Oly, with your new soil mix the foliar feeding is going to be a Godsend if you are lacking anything or the mixture isn't competely broken down yet. With multi strain grows this allows you to adjust the nutes to your plant, minor adjustments, so that you are not having to adjust or keep a seperate mix of soil. The fine tuning you can to your individual plants either by concentrations or suppliments is huge. Really, without using this method I would not have 10 different strains and/or phenos going at the same time, it would drive me nuts.
A quick suggestion on the foliar feeding the finer the mist the better the results and the addition of an adherent or spreader is also very important. I found a little atomizer pump up 2 liter for $8 and it has made a big difference with my applications. I was always too damn cheap to spring for one before and it was a stupid mistake for many years.
Good Luck to both of you and keep spreading the good word