I have been looking at the work of James Gurney on Youtube and on his site: (jamesgurney.com), and his blog: (gurneyjourney.blogspot.com). I like his sketching, his sense of humor, and his obvious intelligence.
He tones his sketchbook pages and I tried it in my own. I made my watercolor paper sketchbook and the paper is a bit to rough, but I have since used matte board and a little less rough paper to practice. In the future I will likely try to purchase a sketchbook recommended by Mr. Gurney.
Gurney also uses gouache and casein in his sketching. I have enjoyed gouache before looking at his work, and I ordered casein to try. Casein is a little different to use (opaque), but I have been having fun each day and I find painting small is fun AND fast.
Below is a sketch of a sketch I did at the Crooked Fence Brewery in Eagle while painting with the Nampa Art Guild plein aire group.
This one is Bayberries Florist shop in downtown Caldwell.
Last is a Gouache/casein on matte board. The sky came out pretty great, to me.
The matte board was already a sort of orange color, so I didn't tone it. I did the others. I like the orange/burnt sienna tint best, but I am experimenting. Check James Gurney.