Do you use a particular point shape or is it just a tapered round point on the graver you use? I have read that some people prepare their horns by applying thin CA glue on the surface the kicking it off with an accelerator then a final sanding or buffing the surface with wax. All this to prevent ink sinking into natural fissures in the horn. Your sketching on the horn shows lovely artistic skill, how do you prevent smudging of the graphite while carving. Map horns look great when executed like yours but river maps are the pinnacle imo.
Thanks Richard