Question on this. With my stock I am doing that has 2 coats of my color altered tung oil on it already,,would mixing up sanding dust and my color altered tung oil from a similar color piece of walnut and using it as a slurry cause a issue? I am thinking this...I have 2 coats of my red oil on the stock, now if I mix up some separate sanding dust with my red oil and apply this as a pore filler would the additional tinted tung oil darken what I already have? Would a person maybe want to apply a coat or 2 of straight uncolored tung oil over the stock first to keep the slurry from soaking in and coloring more?
Its hard to explain!!
The more "red" you add, the redder your stock is going to get. If the question is "will doing any of these things alter the color of my stock from where things stand now," I think the answer is that it likely will, but it might not do so to extent that it is "too dark," or to the extent that you don't like it any more. You're the only one who can judge that, but there is no filler that won't shift your color a bit, and all of them require sanding or scraping.
Once you have a couple of coats of oil on your stock, as you do now, additional coats of oil are not going to penetrate any deeper, or darken the wood very much more. (Pure) tung oil does not attack itself in the way that nitro lacquer does, so any coats you add from this point are not going to dissolve the cured red coats you already put down, (as long as they don't have solvents added, like in that recipe you posted.) Cured tung oil is more like polyurethane, in that respect.
Still, anything "colored" that you add to the pores is bound to shift the overall color somewhat. In this photo, we can see that the pores in the open end grain look "black." They'd probably look different if the light were coming from above. If we filled them with something other than a very dark (i.e. black or dark brown) filler, they'll look lighter, the overall effect from a few feet away is liable to be "lightening." At the same time, they'll look darker if filled with a dark filler than they would in this photo if the light were coming straight-on:
If you look to the left, at the face grain, you can see the dark lines that result when walnut capillaries have been exposed sort of axially. You probably have lines like this in your own stock, since gun stocks are usually made from plain/quarter-sawn blanks. The interior of those pores is darker than the surrounding "solid" wood, probably due to minerals or spalting or something. I don't really know, but walnut generally looks like that.
Obviously, opaque white filler would lighten those lines, and opaque dark filler would darken them. I would venture that "red" filler that's made from sawdust would lighten them -- their dark walls would be obscured, and there would no longer be any shadow in them, and the overall effect (from a few feet away) would be one of "lightening."
I would caution though that if you take from this that you should use a darker filler, that might require some extra sanding... unless the tops of your capillaries/pores are very sharp and truly "square," I can imagine the filler sitting on top of those pores in a sort of "golf tee" shape, as the filler sort of flares out at the top where the top corners of those pores are rounded over. I think this could have a fairly marked effect on the resulting overall color, whether your filler is red, or otherwise.
That would usually mean more sanding, to get down to where the tops of the pores are sharp and square -- something that is almost certain to disrupt your existing color. Oil finishes penetrate pores, or course, but they don't penetrate the solid wood nearly as far, and it is not going to take much to sand through your color, or at least lighten it.
If it were me, I'd wet-sand the stock with red oil, and continue to use it for some (if not all) of the subsequent coats. That's your best bet for getting a uniform color, I think -- trying to avoid sanding your existing color is making everything way to dicey and complicated.
If you wipe the stock down thoroughly (after waiting a half-hour or so for the oil to start to set-up) after each coat, you won't add much (or maybe even any) new color to the top surface of the wood. Most of it is going to come from the first couple of coats.
