Ahrends Grips
Here is what I do, I have been very pleased with results and have been asked how I got them so nice.
I have Stock conditioner from Birchwood Casey, I use that rather vigorously
several times, then I use their GunStock Wax.
I think they come out great.
I am attaching a quick photo that shows a new pair I have not played with yet and stocks on a gun that I have.
I am guessing the wax and the elbow grease is most important, but stock conditioner makes it go faster. I would guess that car polish might work too, or anything really ,really fine and yet abrasive. I bet Renaissance wax and their pre cleaner would do same thing too.