A mistake I see repeated here and there is sanding the wood with the [supposedly] flush inlayed parts removed (tang, trigger plate, buttplate, toe plate, patchbox, barrel key or pin escutcheons, nose cap, et al). You want to finish the metal and the wood together at the same time. Use a rigid sanding block, so the metal doesn't end up proud of the wood. Always use a sanding block until you're done with the finest sandpaper you'll use. Then do your 0000 steel wool, to where you're ready to apply the wood finish, before removing the metal. I've seen some apply the wood finish [stain at least] with the metal parts in place too. Any scrubbing of the stained wood is done with the metal in place. With walnut you may not be using stain, but you get the drift. If you're using a hardening final finish, remove the metal before it hardens. Don't get any build-up in the mortises or the metal won't go back in all the way unless you scrape it out, which presents its own dangers.
Working on the wood with the [supposedly] flush metal removed will round the edges of the inlet mortises, yielding in a not-so-great result. Don't do it. If you do everything right, you will scarcely be able to feel the interface between wood and metal. You blue or brown your metal inlays last.
I've seen silver and nickel silver inlays left in place all the way through to the end. They're carefully buffed after all the sanding and steel wool, then the final finish coats are applied.
I've seen some otherwise pretty well built rifles ruined (in my opinion) by failure to understand that simple concept.
Also look up "whiskering" of the wood.
There are many different techniques, so take a look around and see what looks best for your project. Track of the Wolf, among others, sells instructional books and DVDs on this stuff. They're worthwhile.
Probably the best advice of all; Do not get in a hurry. Take your time.
When sanding, avoid edges you want to keep crisp - don't roll over the edge, rounding it excessively. Then again; a really sharp edge is too vulnerable, and can even splinter, so you want a nice, little, consistent radius on any outside corners. That sort of thing is the difference between a cheap looking job and a really great one, and just paying attention is the key.
One of the easier finishes is a drying oil. Linseed oil and Tung oil have been used a lot, but I've gotten some spectacular results with 5 to 7 coats (more or less depending on the level of gloss you want and on the porosity of the wood) of "Danish Oil Finish" with 600 grit wet-or-dry paper and 0000 steel in between coats. It doesn't protect real well against direct rain and the like, but it is very easily "fixed" by rubbing in another coat. You flood coat, let stand a bit, then wipe it off and let dry for a week or more. Yes; it takes time. Then again, a sprayed coat or two of a good satin urethane has been known to look pretty good, but you'd need a very dust-free environment. That's another great thing about the Danish Oil-- dust is hardly any issue at all unless you're very careless. A more traditional finish on a flintlok is a nice touch anyway.
And that that point I have risen to my level of incompetence.
Whole books have been written on this stuff, so get one of the books. Ideally you should be reading up, and experimenting, while waiting for your kit to arrive. Messing up on a piece of scrap, or an old file handle, etc., is a lot less painful than mesing up an otherwise decent kit gun. Don't rush!
