Acoustic Guitar Construction

What can I use to bring out the wood grain before I apply any finish?

I am working on the back and I would like to see the grain stand out before I apply a finish.

At this point in time I am planing to use Watco Danish Oil and a wiping varnish.

That might change but it seems the easiest for a beginner!

What wood is it, John?

Do you plan to use a pore filler?

The wood is walnut.

I plan to pore fill by wet sanding with the Danish oil.

On the back and sides i am thinking I would use a wiping varnish.

Not sure what I will do with the top.

This is my first guitar and it is somewhat modeled after a Fleta Classical.

You can fill the pores with a very dark filler or just use Zpoxy. The latter is almost clear, but it brings out the grain very well.
On non porous figured woods I stain the bare wood, and sand that completely down to the wood again. In the pores a little color is sucked in and that makes the grain stand out.
Herman

I agree with Herman. Sanding in the walnut will do more to muddle the grain than bring it out.

Are you going to attempt a high-gloss finish? It's a matter of what you want - please remember that a high gloss is not a necessity for a beautiful finish - though it certainly looks nice if it's well-done.
Lowden and some other makers go for a nice hand-rubbed sheen, which can really show that grain. A coat of Tru-Oil as a sealer will pop the grain very well, and it's been my experience that even if it is 'sanded in', the grain continues to look good. Always practice on scrap, no matter what method you use, so you won't be disappointed with your efforts.