At this stage I'm finished with all the airbrush work and I'm starting to push those last details. I did all my airbrush work with acrylic paint, so it's no problem to go back into things with light washes to polish out details. I'm approaching 90% of the highlights with white gesso. It's not very opaque and it has a translucent quality that heightens the color beneath it. Plus it has a great chalky yet buttery texture that is both easy to work with and gives great results.
I didn't put any color on the girls in the background until the sky was fully in place. I wanted to have a little atmosphere between those figures and the subject.