Drake, there\'s a few different ways to approach this, and what you do will depend on which techniques you\'re comfortable with.
Style 1: Simple Wash/Drybrush
This way is probalby the most straight forward, but you\'re likely to get \"fuzzy\" looking horns.
1. Basecoat your horns with a nice, medium brown like Snakebite Leather.
2. Apply a thin wash of a darker brown (like Brown Ink) around the join of the horn and the head/helmet/whatever, and around the last 1/4 of the tip. (Horns darken as they age, and the tips are the oldest parts...)
3. Drybrush most of the horn with Bleached Bone (or Ivory), leaving some area of the Snakebite near the join of the horn and head. You probably also don\'t want to completely cover the darker tip, but you may want to feather it out a bit, so that you don\'t have abrubt lines.
4. Drybrush a little white where the most highlights would be.
That\'s pretty simple, but it will look a little fuzzy, since most drybrushing tends to do that.
Style 2: Layering
If you\'re comfortable with layering, then use the same colors as above, but do layers rather than drybrush/wash. You\'ll need more steps (that is, more in-between colors) to make it appear smooth, but probably worth it. Just remember when layering to keep your paints really thin!
Style 3: Blending
Probably the most difficult, but will likely yield the best results. Wet-blending here is probably not too difficult, if you\'re familiar with the technique. A good retarder is really needed, but you won\'t need as many in-between colors, since you\'ll be mixing them on the horn itself.
Personally, I\'d go with somewhere between 3 and 4, with my pet technique. (Cue: U4-Welcome to chime in and mention my fave word...

)
I see that you\'re in Seattle, too, Drake. PM me, and maybe we can hook up at some point and do some painting, especially if you go to Game Wizard any time.