Powder feeding is a one part whole grow powdered feed.
There are four different powders one for indicas (short Flowering) sastivas {long flowering} Hybrids (hybrids) vegetative growth and mothers (grow)
When using in small amounts I weigh the amount of grams I need on digi scales, when using larger amounts I use the 10 gram measuring spoon.
I still use cal/mag as a matter of course and in the flowering phase I use an additional PK booster and back down the amount of powder feed.
weigh the amount you need add to water, mix, PH it then check EC and water in the feed.
I have only used it for one grow so far and had good results.
I will continue to use it as I was gifted 2 Kg's of it (short flowering) and I don't like to waste things.
I have been an organic grower for many years so it is a bit weird for me to be using this, but times are hard and it was gifted to me so I a using it.
Once it has been used up I'll go back to organics, it is what I am comfortable with and it is better for the environment.
If your not an organic grower and want simplicity and want to get good result then give it a go.