Look at you, brave soul, venturing into the emptiness of mograph.net
A while back I was watching a concept artist doing these amazing paintings, thinking I'd love to do that, and I had that same thought of "oh, I gotta get my hands on his brushes cuz that's where the MAGIC is, BRO! Can't do it without those brushes!" And he'd repeatedly say "it's not about the brushes". And of course everyone who watched wanted to know about his tools and brushes, so he finally gave in and made them available, and I grabbed them. And the set was even organized into numbered groups in a clever way, so props to him. But I never use them! They're fashioned from his process, not mine, and that was his whole point.
So in all honesty, I just use a plain ol' brush with the hardness set to 0 most of the time, and I size it as needed. I use that for painting masks, adding light spill, you name it, that's almost always what i'm using. Exciting, right? RIGHT, BRAD?!!!! CAN YOU HEAR ME? Oh I forgot, this site is dead.