FWIW, years ago I acquired one of those old carving knives that you often see at flea markets, etc., with a bone or antler handle that looked like it had layed outside in the sun and rain for a long time. it was fairly rusty, but cleaned up decently (and was stamped Sheffield) and I almost just broke the handle off to redo, but then I decided to scrape down that weathered old handle to see where I might hit solid material. The top surface came off pretty quickly, and once I hit denser stuff I went to my drill press mounted rotary wheel. I ended up with a good coffin shaped solid, but dry handle. Baby oil was sucked up, and it took a few evenings of rubbing some in, but that handle is the nicest deep golden brown, honest aged look that you can imagine.
I made it into a dag, and the cut off tip became a patch knife for a good friend. The steel is magnificent too.
I mention this because Ive become fond of using finishes that enhance the natural grains and material, rather than staining to something else. Sometimes some blending of colors is needed, though, and your preferences may not be mine. When needed, I like alcohol based leather dyes.