Here is a tutorial by Stuart Semple on how to use his Black 3.0:
BLACK 3.0 is the blackest and mattest acrylic paint on the planet! Unlike other super-black coatings it can be safely applied with nothing more than a brush and usually in one coat, no toxic particles or technical spraying - I’ve also worked super hard to make it affordable.
To get the best finish:
Use a nice soft brush (not a rubbish scratchy comblike one)
Apply at room temperature 10 - 25 c ( 50 - 77 F)
Use as little paint as possible and spread it out nicely
If it's put on too thick the paint won't dry properly and could crystalise
Allow to dry between coats (at least two hours, overnight is better)
Use a hairdryer to get max blackness
Seal absorbent (porous) things with 25% PVA and 75% Water
Prime shiny (non - absorbent) things with primer or Black 2.0
It was made by artists FOR artists just like you! On top of that, my studio is non-profit, so all of the money raised selling any of my art, paints included, just goes right back into the studio for the next art project.