(Link to YouTube) I want to show you how to paint a sunset light effect. I start with a watercolor sketchbook primed with a tint of Venetian red casein. It is OK to use acrylic paint or gesso for the priming also.
I paint the sky with white gouache. The darks are mixed from ultramarine blue and burnt sienna. All the shadows near the setting sun are part of a large gradation that transitions through orange colors into browns and grays.
Most of the painting is done with a 1/2 inch flat synthetic brush and a very small round brush. I ignore the actual colors and reduce everything to two values. The key to this approach is the intentional sacrifice of detail in favor of a larger light effect.
The tutorial Gouache in the Wild doesn't contain this painting (which I did two days ago), but it has other gouache paintings done on location.