Such fun. Need to do several more with different colors. I didn't have Payne's Blue Grey and while you suggested not using a granulating paint I tested out my Sodalite Genuine which had low staining characteristics and lifted beautifully on my scrap. It is harder to work in some regards and requires you let the paper dry completely before layering more otherwise I just find that it will scoot away from the wet brush when you touch the paper.
The reddish hue at the bottom of the picture is due to poor lighting and not any extra color I added.
I also don't have any gouche so grabbed my handy posco pen. Only problem with it is that you can't really blend it with underlying paint. You can lift it a bit, but it is pretty unforgiving.