I learned the basics of this technique from Bruce Bump's posts. It works really well.
Sand the wood as fine as you want. Walnut is hard enough that you can go to a very high grit. Apply the oil in thin coats and sand it in with a fresh clean piece of paper each time. This will help the sanding dust fill the pores. Allow each coat to cure, lightly sand off any excess and do it all again... and again... and again. This may take a few days.
When the wood just won't soak up any more oil, give it a final light coat and let it dry, then burnish it by hand with old, soft denim. Don't be too gentle, moderate friction and heat are your friends in this case. It likely won't get as glossy as stabilized wood can, but it will have a nice shine, and a lovely warm "glow" that showcases the natural chatoyance of the wood without being gaudy. It will also feel warm, comfy and "grippy" in the hand.
I don't know if a buffer is a good idea or not, I never tried that. See Rick's comments above.
Hand-rubbed walnut and maple handles are my all-time personal favorites. I think you'll like it. :thumbup: