Generally with any method of aquascaping whether it's NPT or something else, using a ton of plants right from the start produces better results both aesthetically and for algae control. I've seen some stunning scapes that had only gravel as the substrate and liquid fertiliser applied periodically.
Not sure how much of a terrestial gardener you are but you can treat the hairgrass like any pot bound plant you get from the nursery. Just tease it out gently or divide it by cutting. You need to encourage those roots to spread.
I have successfuly made my own root tabs by wrapping a tiny amount (say 6-8 pellets) of Native Plant Osmocote in a bit of unbleached paper towel and shoving it into the substrate. The paper is really there to hold it together while you're shoving it in. After that it rots away under the substrate while the Osmocote slowly releases.
To be honest I would just keep it simple if I were you. The design you've started out with will look good if you just stick to hair grass growing around rocks. So get 5 or 6 pots of hair grass or however many you reckon you need to spread out through the whole tank. You also need 3 rocks: small, medium and large that will give your design some structure. Just plain gravel with no root tabs or anything. But perhaps use some liquid ferts and liquid carbon. And do weekly water changes.