I've used concentrated laundry soap and a nylon brush in the past. I have also used "Tek" solution; this works better, but I don't use more than a couple of capfuls of it. Scrub the antler in this "soap bath," then immediately take it out and rinse with clean water. To restore the "natural" stain appearance, apply a thin coating of linseed oil. This gives it that natural luster.
Daniel E. Schmidt, Editor, Deer & Deer Hunting