This is another of my paintings from the Tim Horn workshop near San Francisco. I really liked the shadow shapes on this curved road. I also liked the stop sign, but it took a few tries to get a red that didn't take over the whole painting. I made it much lighter and more orange than I thought originally.
I found that for all my paintings from the plein air workshop, I wanted to do a little touch up back in my studio. Mostly I focused on big shapes: making the shadows clear and how to make the forms read using value and color temperature. As Tim said, if you're not happy with your painting, the problem probably isn't in the details.
This is the first exercise we did in class, which focused on just that. Tim had some big cardboard boxes that he had painted primary colors, that he put on the gray wooden deck. The exercise is to show how warm sunlight and cool reflected light (from the blue sky) affects the values and color temperatures of an object. The top one is Tim's and the bottom one is mine. It's always easier to paint when someone shows you how!