Das Update:

OK, I decided to say the hell with it and use the digital camera shot as the base for the final drawing, rather than scan it.
Things of interest:
--I decided to use a coloring technique that I've never tried on any scale before, which is make base layers of color and stacking multiple translucent layers of tone on top of it to produce a shaded effect.
--I tried it and decided that I didn't like bright red skin. Pearly white skin is far more sexy and demoness-like, in my opinion.
--Right now, if you can't tell, I've got her right arm down to her wrist, neck, head and hair (excluding hair clip) done-ish. No eye or eyebrow yet because they were looking cartoon-y. Her hair color can very easily be changed, but right now she's got Asuka-Hair and is also pretty plastic, whick I will fix.
--The Horn right now is a pale pink. Why? Because I was of two minds with it. I kind of liked the idea of a red horn, which would stand out, but I also realized that the horn would be bone, and couldn't come up with a reason for it not to be bone-white. Likely to change, but right now a testiment to my indecisiveness.
--The final product will not have those solid blank contour lines, but rather very soft tonal areas that look like shading but help the brain wrap around the idea that there is barrier there. Look at the area between her arm and her breast for a good example of this. In the end, it will look more natural.