I'm painting a portriat of two people, both are smiling. The photo is a wallet size and the painting is 24 by 36. I can not really see there teeth, but want them to look as natural as possiable. What colors are normally used..besides white? For the shading and for the lines between the teeth? Any tips on shaping them or anything will be apreciated. I normally do not paint from photos showing teeth, so this is new for me.