Are you in coco or soil? The living soil method isn't as effective in coco and could be more effort than it is worth. Sorry, don't know who distributes over there, but I can ask a few friends and see if they have suggestions.
My personal experience with dry amendments has been mixed. For outdoors, long use soil, I love them and building the soil and creating the soil food web. But indoors, in a container for 90 days, it can be tricky to get the ingredients active at the right time if they are slow release. I've also had the experience where the dry amendments didn't dissolve very well in water and that formed a crust layer of hydrophobic soil. Indoors, I prefer my bottles, outdoors, I'm using as much of nature as I can.