I do stock work for a living, so I get to use a lot of different products. Here's my take on finishing:
* Sanding wood beyond 400 grit is a waste of time, it will make no difference in the finished product. Once the finish is dry and you are sanding for final finish, go ahead and sand to 500 or 600 if you like.
* TruOil is very easy to use, but does not truly seal the wood. If is easy to apply, and if it is scratched or damaged it is easy to touch up.
* Permalyn is nice, it is a polyethylene-based oil finish, so it goes on like oil. Very easy to use, very durable. To touch it up, just sand, then reapply more Permalyn.
* Brownells' Acra-Wood finish is very durable, easy to apply, and is the most durable of all the finishes. Spray on several coats, sand, apply a few more coats, etc, until it is completely finished.
* Various teak oil or tung oil finishes are available, but most are just poly finishes that give the look of real tung or teak oil without the waiting a week between coats for the finish to dry. The biggest issue I have with these finishes is that many are not solvent-resistant. If you opt for teak oil or tung oil, buy products that are specifically recommended for firearm finishes.
* For staining stocks, use spirit-based or water-based stains. I use water-based, primarily because wood is water-friendly, and it is easy and very forgiving to use.