The "RFRF" pen is highly pressure-sensitive and has no anti-aliasing, being intuitive and simple in both design and use.
The "sketch" brushes allow for more nuanced values and shading. I strongly recommend experimenting with different radius sizes and particle-density values, until you find a combination that best suits your work.
Recommended use on 4000px canvases.
Credit for using these brushes is appreciated, but not obligatory. Please enjoy!

Both sketch brushes also have anti-aliasing OFF by default. If you work with canvases smaller than 4000px by 4000px, I recommend turning anti-aliasing ON.
Brushes