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After the background, I add trees. White lines that are thick, thin, and anything in-between.
These are going to be white bark Birch trees. A few stray thin lines for branches, and the trees are in.
A light gray painted down the side of the trunk and branches for shadowing. And finally the distinctive black marks in the bark which makes a Birch look like a Birch. Easy, yet very impressive.
One more additional step before this painting is complete.