I have added another layer or two to this painting. I think that it is almost done. The darker backgraound has created that sense of intimacy I was looking for, but I feel like the skin on both girls could be warmed up a bit more.
I have been using Nupastel to define lines and highlights, and matt medium to lay in transparent glazes of colors - usually the colors are transparent themselves - such as sap green or alizarin crimson, but the last layer I was using a pinkish magenta and a baby blue to create the lavender, which was more opaque, even with the medium mixed in.
All of the texture of the original gessoed layer still shows thru - even more so now that some of the glaze has settled into the crevices. I think it's almost done!
See gesture drawings from this session here
And the previous stages of the painting here