Sometimes, you take what you can get. In this case, Diane and I were lucky to have survived the blazing August heat a couple of years ago. We were there to demonstrate during a Main Street sidewalk merchant's event. I'm afraid just about all the passersby could glean from my work that day was the disintegration point of linseed oil which streamed down my canvas as I worked. Diane, the great trouper she was, had to continually excuse herself to wipe the sweat out of her stinging eyes. That's what I call "painting on the fly".
I finished the painting in my studio, using a photograph. I like how it turned out, but you can see the strain in her expression. Not an optimal result for showing. The best case for my purposes is to somehow secure a momentary glimpse of the subject in a context of something specific. It's rare to have a model who can pull that off live, though, so I wind up working from my photographs quite a lot. While doing so is not well regarded in the art community, it's the only way for me to have "non-posed" expressions and body language in my paintings. The painting you see next is a good example.