The softwares I use to draw are FireAlpaca and GIMP, then I'm looking for a solution that can be carried out on those softwares. Thank you in advance for your suggestions !
Without more information, I can't comment much on this particular brush, but most "anime" brushes I've encountered are just captured dabs set to rotate based on the direction the brush is going. The brush is likely not square in its dimensions, with the "direction" side being longer. The edges are semi-transparent, and the interval between dabs can be adjusted to make it more "sketchy" by not having them cleanly meld into each other when switching direction or increasing velocity.