If you want to skip the guesswork, replicate these exact values:
SAI 2 allows Vector Layers (Layer > New Vector Layer). Here is the professional workflow: paint tool sai 2 lineart brush
This will give your lines a "scratchy" quality that looks fantastic for horror comics, watercolor styles, or illustrations that need a vintage feel. If you want to skip the guesswork, replicate
Brush (Fake Pen) Size: 5.0 Min Size: 0% Density: 100 Stabilizer: S-7 Hardness: 100 Blending: 0 Opacity Control: Pressure Size Control: Pressure paint tool sai 2 lineart brush