Braintan-
a agree with your hesitation to take a Dremel to horn... just too much opportunity for a devastating 'woopsie,' which will inevitably happen at the end of the project and spoil a bunch of otherwise nice work. the only time you want to take a power tool to it is to drill the pour hole and to square up the butt (i use a belt sander, and do that outside).
additionally, to ensure domestic tranquility, i would likewise avoid taking anything hot (the previously mentioned heated iron rod, etc.) to the horn, which is compressed hair, and will smell just like burning hair if you get it too hot, on account of you'd be burning hair and that's what it would smell like. so, what does burning hair smell like?... well, it has go- sleep- on- the- couch written all over it. (luckily, i was outdoors when i made this discovery and saved a spell of couch sleeping.)
a set of inexpensive woodworking tools will hold you in good stead, especially if you're willing to put up with less than stunning fit&finish, and especially if you don't mind spending the afternoon putting a proper edge on them and then stropping them on a bit of heavy leather. some people put jewelers rouge on the leather and some don't, and there is a good bit of debate about it. i do, but you should do whatever works for you. (if you do a bit of clever cutting, you can strop the inside of the gouges, too- this makes thing all the much better).
good luck with your project
msw