My first step was to cover several boards with gel medium and make marks on the wet gel to create texture. I realized this was going to be expensive, because I was using a lot! So I pulled out the wall patch compound and used that on some of the boards. I have one that has an acrylic base, which is important. Without that, it will crack off the surface when it is dry. At least that has been my experience using it on the edges of canvas.
Beam recommends illustration board, but I used mat board since I have a lot on hand. After the medium/wall patch dried, I applied gesso so I would have a nice surface for painting. Below are a few of my textured boards, ready to paint.
Scratches with a bamboo skewer
The medium was squeegeed through a piece of heavy lace. Can't really see the lace pattern, but it has an interesting texture.
Here I used a spring whisk, part of a plastic ceiling grid and a skewer.
This is pretty much like using the sgraffito technique on flour paste, so I felt right at home creating these backgrounds. Then I laid the first wash on one of them. That takes me back to my watercolor days. I love the soft effect even more with the textured background. And when I paint over it, those colors won't bleed into the 2nd layer.
It's a slow going process, since I only have a short amount of time to devote to this right now. But I like working in stages like this. And I know they don't look like much, but I am having so much fun doing this. The neat thing is that I don't really care what the end result is - I'm just enjoying the process!