For this painting, instead of outlining first, I started by coloring directly, planning the whole picture first, and then gradually proceeding with detailed descriptions. At the beginning of the coloring process, I divided the area into two parts: the light part and the dark part. I ignored all the details and kept the division as simple and straightforward as possible. I think it's important to maintain the shape of these light and dark areas until the painting is completed without significant changes.
Of course, as the depiction progresses, the boundary between the light and dark areas changes in various ways. Nevertheless, the overall framework does not change. Although I haven't fully understood it yet, if the initial framework is significantly altered during the depiction process, the foundation of the depiction built up to that point will change, making the painting feel awkward in some way. In other words, the initial framework of light and dark should evoke the form of the subject you want to depict. Alternatively, the initial framework should be able to fully convey the content you want to express according to the composition of the painting. Perhaps, the initial intention remains as an afterimage in our minds.
I've separated the coloring process into different layers, so checking the file should help you understand better.