Step 4 - When I have the shadow area of the tree the right shape, I make a thin wash of a yellow - you can use a cool or warm...whichever suits the color scheme you've chosen - and I wash it over the white part of the tree, dabbing with a paper towel here and there to keep some white, and not have it a completely even wash. I carry the wash over the edge of the shaded part too, but not over the whole thing. Gets too muddy.
Step 4 - light yellow wash
Next, I mix up a really dark dark using Fr. Ultramarine, Burnt Sienna and maybe some of the red...really nice and dark. I use this to define the knots and things. I like a lot of contrast in my trees, but you may want to do it lighter...it's your tree after all. Just dab it on using lines, dots and smudges until you like how it looks. Remember to make sure that there is variety in spaces between the dark areas, and variety in the shapes. It's easy to forget, and do the same shape over and over again. I usually have to go back and change things to keep the variety.
Put some dark lines and dots on the light side of the tree too, making sure they follow the curve of the tree trunk.
After I add the darks, I go in with some pure color...Cad Orange and Aliz Crimson. I put quite a few dots and lines of it around the darkest parts...it's about the same color as that fungusy stuff you see on trees...and it looks fantastic next to the dark blue!
Then I hop around with a brush of Aliz Crimson, putting dots and lines here and there until I like it. I also go in with some pure Fr. Ultramarine, and some more purple, adding it where it's needed.
The last thing I do is, using a very small brush and some purple, make little dots along the area where the shadow turns to light. From a distance this helps the gradation from shadow to light look a little more gradual. I put in dots of different colors just to make it interesting close up too.
And that's about it! You can fiddle with these until the hairs fall outta your brush, always finding another spot to put in more color...but really...it's done!
I hope you find this of interest...and of some help. If you have any questions, please ask. I've likely forgotten something...and if I don't know the answer...I'll make something up!! Aw...just kiddin'...
Please leave me a comment telling me what you think of this demo. It will be very helpful to me for teaching my watercolor classes. I want to do a good job. Thanks!