Step By Step
Create New Brush Tip
Straight Line Tool → Select Dotted Line in Brush Shape → Draw the line → Register it as a Brush Tip Shape.
Replace Brush Tip
Duplicate the brush you want to customize → Open Advanced Tool Settings → Brush Tip → Material → Remove the original brush tip and replace it with your newly registered brush tip.
Additionally, my favorite brush set recently, II2 Water Brush Set (ID: 2282079), is still available for free. These brushes are excellent for rendering in general, and for rendering hair and clothing in particular, so I highly recommend them.

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