So I stripped that walnut stock from the REM 788 that I picked up and I have it stained.  A good job (if I do say so myself).
Now I'm stopped because while I have refinished furniture, I have never refinished a wood gun stock.  What should I use to lay on the coats and get that deep luster like the really expensive custom guns?

Since you’ve stained it, I assume you’ve already raised the grain and cut it down.

While not absolutely necessary, you probably should fill the pores with a wood filler.

After that, (if it was me) I’d put on several coats of Birchwood Casey Tru-Oil, which is linseed oil with driers.   I put it on with the palm of my hand.

I’d then cut the sheen down to an eggshell finish with Birchwood Casey Stock Sheen, which is a mild abrasive.  I use a cloth rag for this.

Don’t forget the tack rag!

I have used Tru-Oil with good results.  Birchwood Casey sells a kit with a stain/filler, oil, and wax.

Now I am partial to using Behr's Tung Oil finish.  It's relatively cheap and as easy and forgiving as Tru-Oil.

The main ingredient you will need for a deep finish is patience.  Wipe stained stock with tack rag, apply oil with hand or rag (hand is more fun) and let dry until no longer tacky (1 or 2 days.)  After a couple coats, you can use fine (600 or 400 gr) sandpaper to lightly wet-sand the oiled stock.  Use more oil with your sandpaper, and wipe the resultant sludge to fill open pores.  There are plenty of instructions for this on the web.  Mainly, use lots of patience and never apply a new coat on top of an undried one.  Final product will have lots of gloss.  This can be cut with mild abrasives (polishing compound, steel wool, etc.)

Avoid Minwax products like Satan's own seed.  Even their so-called "stain" sucks.

I used a minwax stain followed by many coats of linseed oil on a Winchester model 52 stock.  Turned out great.

I don't recall the variety of stain, but it was a deep red.  Over walnut, it looked spectacular. I steel wooled and oiled the metalwork to remove rust.

Before:  Scratched varithaned stock with reddish surface rust on the barrel and receiver.

After:  Dark reddish walnut that smelled of linseed oil, Shiny metalwork with little pitting that showed good careful use of a good rifle.  It's now a keeper, sold as a dog.  

EDIT:  I heard about a Beeswax and Turpentine mix used on rifles - supposedly this will fill pores as well and give a non-slip grip to the stock.  This may be the rifle I try it out on.  

I've refinished 2 different rifle stocks before and used Tongue Oil on both with exceptional results.  I used Homer Formby's TOngue Oil.  Just found out that there are 3 different gloss level products you can choose from.  

I chose the "standard" finish and am quite happy with it.  I guess if you like the realy glossy look you could get the "high gloss" Tongue Oil.  

The tongue oil is a very thin finish that actually penetrates the wood yet doesn't give the stock that glossy-thick look that a polyeurathane finish would.  It's also very easy to apply and needs only a very light wiping with super fine steel-wool in between each coat (and after the last).

Good luck.

CMOS

I've used the Birchwood Casey kit with good results. Just follow the directions. Since you've already stained it, you wont need the walnut stain that comes with the kit, but the kit doesn't cost much and it has everything else you need. Like ken_mays said, allow time for drying between coats.

Quoted:I used a minwax stain followed by many coats of linseed oil on a Winchester model 52 stock.  Turned out great.

<rant>
The biggest sin that Minwax is guilty of, IMO, is that they are unable to separate "stain" from "varnish."  In other words, you'd better be happy with the first and only coat, because it seals the wood and further coats will not darken the color, they will just make it a sticky gummy mess that will take about 2 weeks to dry.  

Plus, if you want a "built-up" finish, Minwax won't let you do it.  Their attitude seems to be, "hey, if you want gloss, slap on some polyurethane."  Anything approaching a hand-rubbed, deep finish is not going to be achieved this way.  You *can* apply a multi-layered oil finish on top of Minwax-adulterated wood, but only after it dries for the better part of a month.

As long as you realize that Minwax is geared toward the folks who only want to put some sort of finish on their pine baseball cap racks or tater 'n' onion bins, you'll do all right.  If you really like a decent finish on your gun, you'll probably want to avoid this "Cheese Whiz of Wood Finishing Products."  
<rant off>

That said, they have a red stain that is pretty damned bold, and works well on tater bins.