Most of the time you want to follow the natural directions when placing brush strokes, but it is an artistic choice, you may have other ideas. Already in PostworkShop 2.1 you could limit the number of possible stroke directions in the Random Painter.

For the special case of a single stroke direction PostworkShop 3 adds the new “Direction rotation” property.

Of course you can combine multiple layers with different stroke directions to create a “rough background + detailed subject” or a cross-hatched look.