You mean that black charcoal effect?
You can ask him personally on Reddit
But some of the Kyle Webster brushes do pretty much the same thing
Thanks for the above I have some of his brushes but I'll check more out of his.
(yeah is is the black but if you look at the red colour or all of his paintings that brush is used 99.9% of the time).
I've searched around for ages trying to find the same or similar to that brush/brush marks he uses but just can't find it.
I did send him an email last week but I've had no reply, probably doesn't want anybody using them!?
I'll see if he will respond on Reddit!!