I use Trewax. The one for floors. If it's tough enough to walk on it should be ok for the gunstock, and it works well on the metal also. The only problem is if you get it in checkering it dries white. For that problem I simply apply a thin coat to all checkered areas then buff with a horsehair shoe brush which gives a nice sheen to checkering.
They also make a tinted version that is a beige-very light brown color which I am currently using.
Neither of these is as expensive as the Renwax and I can find in most good hardware stores, and get several pounds for the price of one Renwax.
