Both natural material, so they both need to be cared for. Mineral oil soak is good for both periodically. Have heard that Hooflex is good for the horn. I personally think that horn needs more care, I have no facts, that is just my personal opinion.
I usually do this treatment once when I get the khukuri, and then once a year.
3 day mineral oil bath, apply Boiled Linseed Oil (BLO), sand lightly with 4-0 steel wool, apply BLO, and sand again (do as many times as necessary) to get a good smooth surface and sheen, then stop and your done.
If you have a buffer, buffing horn with red rouge, will really make it pop! after the mineral oil treatment of course.
I believe pugs and some others have mentioned the above techniques, I've used them, and they work extraordinarily well.