For the shape I guess you can use pen tool to make it...
and for the grunge patterns, as the artist said, they're made with brushes...

http://www.deviantart.com/view/506174/

nah... let's say you have a watercolour brush, can you draw this in one line by just simply control the pressure? I don't know if there's any pro here can do that, but I'm a tablet user too and I found it's not so easy to control... the pressure detection is only used to make it realistic, but not to draw something 'artificial' like this...