Minwax Wipe-on Poly (oil-based) is water proof and very durable. It is available in satin and gloss. Will go over stain easily. If the pores are already filled, it is ready to coat. If not use it to do this:http://www.woodworking.org/WC/GArchive99/1_20waltcunfin.html There is no better wood finish out there.
RAN
Minwax Wipe-on Poly is good finish and I use it for a number of things, however it is far from "waterproof" and there are many finishes better for waterproofing.
Never use anything other than gloss for any surface you want to be durable. Powdered silica is added to the satin and semi-gloss versions. As the top coat dries the silica within creates a rough surface to break up the gloss. It makes it significantly weaker and less "waterproof." Use gloss and rub it down with Scotchbright pads or rubbing compounds to your desired level of gloss.
If applied to unfilled wood surfaces repeatedly without sanding the mud into the pores it produces a far better finish than pre-filling or sanding in the slurry, especially in an application like typical military, open-pore walnut.
Because of the tremendous numbers of applications there are many situations where different woods do better with different finishes. For a lot of applications there are many finishes far better than MWP. I would not use it on a stock personally. I do use it on very fine-grained woods in quantity for interior uses. It is a good finish.
