I’ve sort of given up on the idea of ‘the underpainting.’
It does a disservice to the painting process when the beginning of the painting is simply referred to as an underpainting as if the real serious painting will start later.
We might say ‘i just need to get the underpainting in. This is just the underpainting. I will figure it out later.’
The muddled brush strokes, the working it out, the fine edge, and the soft cascade of color that pours out of your brush: they are all just part of the process of making the painting and no part should be dismissed or approached with less presence.
Every brushstroke of every layer is the painting. There’s no part of the painting that’s not the painting. Every mood and moment matters to the finished piece. Study your brush strokes.
Certainly there is a last and final brush stroke. Perhaps everything is underpainting to that final brush stroke.