The easiest way of mixing hydroponic nutrients, is before pouring them into the water tank. Once the nutrients are mixed it really doesn’t matter what growing medium or system they’re poured into, only that the ppms are appropriate for the plants feeding.
Nutrients can be mixed exactly the same for soil, coco, rockwool, hydroponics and aeroponic systems. Plants have the same nutrient requirements regardless of the medium in which they are growing. Yes, some places on the Internet say it’s different, but its not.
One thing that is different for hydroponics, that you don’t need to worry about with soil, is pH. When growing hydroponics, make sure that you monitor the pH of the water frequently.