Pinsel für Hautfalten in gezeichneten Portraits erstellen - mit Schattierungen

I have run into this problem before.  If you use an outer area that is blurred and lower opacity, it still paints fully black because each stamp of the brush overlaps.  So you need to make the shading part very thin like below, and experiment with spacing.  You also need to set angle jitter to Direction, which leads to another problem, that being spokes in the outer shading on tight curves.

Even with spacing set to 1% the spoke effect is still evident.

So maybe better to use layer styles

If you want to devote more time to it, take a look at Dual Brushes.  A lot of Kyle Webster's presets work that way, so find something close and reverse engineer it.

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