I think I can help a little. First, you might consider staining the stock pretty dark. I would then try to hide it with oil paint from an art store. You cannot use artist acrylic paint because it has a different look when you are done and apply an oil finish. I have tried and came real close but after the finish it looks like you painted it. Art type oil paint will look fine but your oil finish will dissolve it and it seems to disappear. I put a thin coat of lacquer over the oil and then oil finished it. That worked.
The really difficult part is the painting. I found the best way was to camouflage it for lack of a better word. Extending the right arm and left arm of your "U" toward the butt and maybe one or two down the middle so it looks like you have mineral streaks. That was an example. I don't see any figure in this stock so I am not sure how you would fool the eye. Unless you are an artist then this will be very difficult. Mark Larson did one for me and it was not detectable when he was finished. My work not so much. I hope someone with more experience will come along and help you more.
