Well I kinda figured it out. This was another attempt to paint in my sketchbook. This time I used a different paint. The one I used last time had some mica in it to make it metallic looking and I thought that mica might give the paper more grab. But this time I used a granulating pigment (Graphite Gray) and it worked a lot better.
I drew this fellow in ink and then came in with watercolour to add the shading. I used a light touch, but not too much water and it took really well.
I'm much happier with this one and I think that I may have a more workable technique. Although we will have to wait and see how it works in the long term.
This rooster is pretty good... I kinda wish I'd used him for a post card. (well I guess I still might - you'll have to watch The Postcard Project to find out.)