I was wondering if this was possible – and yes, it is! I reversed the pressure input of these brushes to create a brush for one line drawings or one-liners or for a different approach on casual sketching wich will lead to more dynamic drawings. Check out the REVERSED_INK brushes (M & S).
Hit the image for this swell sketching and outlining brush for PS.
Here is the watercolor freebie file as plain vectors/images as well as brushes (check available ones in the brushes panel). This should work for you CS5 guys.
I've worked a bit on the combination of a vector brush masking out a seamless texture.
These results are quite cool:
I was asked if it was possible to prevent ugly distortions on short strokes. The Idea was to bypass the the event by creating a vector brush combined with a seamless texture. Yet quite rough but it works quite fine…