On the previous session I re-established shadows in order to perform this stage of "bringing in the light." I did this by glazing Naples Yellow onto areas of strongest light. I also glazed Alizirim Crimson onto black background.
I've been spending roughly an hour on each session on this painting. It looks a little strange at this point, but these preliminary steps are necessary for building luminosity. Going back and forth between building light and establishing shadows and glazing color in between is what oil painting is all about!