I'm sure there are many ways to do it. As has been said a Sharp "U" or "V" gouge can be used but so can a sharp thin short bladed knife. Cutting goes easier if the horn is soft, if you boil it to get it soft you will be able to cut 5 or 6 notches before it needs to go back in the water to soften up again. It is a slow process but will give good results.
Be sure and lay out your design before you get started. A strip of paper cur to fit around the horn at the engrailing point and marked where each notch will be will help. You can tape the pattern to the horn or just mark the horn. Remember that where the two ends meet is One notch.
Another thing that may help is to do the engraining before you shape the neck of the horn. Mark a line around the horn where the engrailing will be. Then about 3/16" below that line draw a second line parallel to it. Cut the first line to the depth you want, then starting at the second line with the point of your tool cut towards the first, the tool will stop when it reaches the other side of the cut. After all the notches are cut you can shape the neck. With a little practice, sharp tools and a good layout the notches are made with one cut. It really helps if you have a practice horn, doesn't even have to be a whole horn just a piece you can layout and cut on.
Tim C.
PS: Or you can use a Dremel Tool but that will probably take More practice. (Can't believe I even suggested that) TC
