Will,
Great minds seem to run in the same tracks ... LOL.
I did exactly what you said ... and used walnut Danish oil to stain the grips ... then coated them with a marine product callled Deks Olje (pronounced ol-ya). The marine coating is more or less half tung oil and half polyurethane ... hella hardy, more or less waterproof, and is the only product that I ever used that would hold up for a year on the decks of my sailboat under the harsh California Delta sun.
The stuff goes on like a tung oil; one keeps applying coats of oil until it the coating closes off the grain, then a light coat every so often for about four hours.
The nicest thing about it is that, if the finish is scratched,one can wet sand it, let it dry, and then re-coat. Unlike varnish, the finish will feather into any scratches.
The Deks Olje I gives a satin finish ... and by adding coats of the Deks Olje II to the top of # I, the finish goes to a high shine varnish like finish.
The weapon in the holster is the same as the one on the rug ... the one in the holster is just after stripping, staining and Deks Olje treatment ...