This is a custom brush I created for my illustrations.
This brush creates very opaque yet still textured lines.
I use it for both lineart and cell shading.
This brush is not blending colors at all.
I updated the settings a little bit over last months, so here is the version I use currently!
Example of use in an illustration I made (as you can see this brush make the lies and shading very crisp):
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Old version