It's hard to say without seeing an example of what you want to produce, but you can try brush variants in the following brush category:
These brush variants, and any others that use Method: Plugin (see the Brush Controls' General palette) only work on existing color, though, so you'll need to remember that if you want to work on a Layer that contains transparent areas.
Also try the following Dynamic Plugin Layers (click the second icon from the left at the bottom of the Layers palette):
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