For scrimshaw I use a awl. I file the awl to a needle point, it makes it easy to scratch the piece of bone that I'm working on at the time. Before I start doing scrimshaw work I get the piece sanded down to the finish I want, then I draw the design with a pencil, then I spray shellac over the piece, after the shellac has dried, then I use the awl to scratch in the design, then I put the India ink on, once I get the design to my liking. I use acetone to wipe off the shellac. This method seems to work good for me.
I've made necklaces out of antler that I done scrimshaw work on.