I'm having so much fun in this sketch style. Even though it looks kinda crowded there, actually the sketch is quite simple. I'm using a new software called Drawpile for this piece. Because of a lot of limitations there, it forced me to think more efficiently. "Just Draw the Shape not Outlines!" my mind told me that.
I have 1 background layer and 1 other layer for the girls. I leave the lighting on HardLight layer above. That's the key.
I attach the PSD file here just in case you are interested in taking a peek