For the underpainting, I combined burnt sienna and ultramarine blue to make a dark, warm tone. Then I carefully followed the charcoal lines, wiping them off with a rag as I proceeded. I used a medium of Liquin and OMS (odorless mineral spirits) in a proportion of about 1:1.
For the lighter areas, I used more medium to thin the paint. I paid careful attention to the light and shadow patterns so I could begin to get a sense of the sunlight on the azaleas and the path.