The skull bone isn't of much use. Cut lengthwise into halves, removing the bone core ( it will likely just fall out when cut)
The horn is solid for the last half of the horn. If the horns are big enough, you can split them and use the solid part as-is for scales.
If you want a stick tang solid handle ( works well with horn), cut off the tip end where it is about 3/4" thick, and then cut off about 4-5" back to make the handle ( usually at the point where the horn starts to curve). You may or may not have a little bone in the fat end. If the bone core is solidly attached, just leave it there. If it is loose, remove it and fill the hollow with resin. A butt cap will hide the recess if there is one.
The above will cut the horn into the solid and the hollow parts.
To flatten the hollow part of the horn into scales, make a flattening jig from pieces of 2X6 and C-clamps. Cool completely for several hours in the clamps before taking out to check flatness.
As for the flattening, the horn needs to be heated up to become pliable. There are several methods. So start with the simplest and work down the list until one works
Boil the halves for 30 minutes to an hour, remove one at a time and clamp between the boards. Slowly tighten clamps. If the horn gets pliable enough, this will work. It may still be too stiff to flatten.
Bake at 240F for 30-45 minutes and try flattening. If it gets pliable, good. If it softens somewhat, try raising the temp 10 degrees and repeat. Go up to 260F if needed.
If it still isn't working, put in a pan of sand and bake at 275-300F for 30-45 minutes.
You may have to repeat several times, and occasionally overbend the scales to keep then straight once cooled. Even then, they tend to warp and twist in sanding if you get them hot.
I am sure there are others who have their preferred methods, and they will add their experiences.
