You need to clean the horn up a lot. smoother surfaces are easier to cut into without the scribe being dragged of by surface unevenness. Having a fixture to control the horn while trying to scrim it, is very important. I use an Exacto screwdriver type tool handle, and one of their hook billed blades, to do the cutting in. That allows me to do the cutting with just the tip. This keeps the rest of the blade from cutting areas I have already done, or marring surfaces that I haven't gotten to yet.
Studying how pen, and ink, drawings are shaded by the number of lines in different shaded areas, will help you a lot to get depth into your work. Good Luck!
Hungry Horse
