Yes, I'll be coating the insides of them. and since I'm the forgetful type, I won't be doing it the traditional way which is to coat the inside with beeswax. (Knowing me, I'd leave them in the car on a hot summer day and have a nice waxy puddle in my car.) I consulted a couple of craftsmen a couple weeks ago at an SCA event who make and sell horns, and they recommended salad bowl finish from General Finishes. I will also be using this on the outside to give them a nice, glossy appearance. So far I've got the insides cleaned out and have the bovine horn sanded smooth. The antelope horn is not getting sanded on the outside. (Looks great the way it is.)
Here is what they look like so far.