1. A brush that paints with clear water applied to pigmented paint that
is already on the painting surface. This would have the effect of
flowing the colors together a little, but leaving some of the original
variation. This is not the smudge tool, which tends to pull the pixels
in way that looks "computer." But rather something that works like the
"Just Add Water" brush in Painter.
2. Brushes that paint dry, with no color, just strokes. This would be
similar to using a dry brush that is pulled across wet paint, adding
brush marks and pulling the paint in the direction of the stroke. This
would be similar to using dry brushes in NaturePainter.