I am refinishing an old Remington 870 stock birch stock. I stained it with a dark cherry colored stain, and then began to apply Hope's 100% tung oil. I had read to wait at least a day before sanding and applying the next coat, though that seems to be a short period of time. However, when I sanded the stock, much of the stain I had applied was removed along with the tung oil (if I recall correctly, I was using 340 grit paper, and I had cut the first application of oil about 50% with mineral spirits).
I decided to restain the whole stock, and ended up staining it several times, letting it dry and wiping down with mineral spirits to remove the tackiness between each coat (I know that multiple coats are generally advised against, but the birch wasn't accepting the stain evenly and this helped me get a fairly even, nice stain). The stock is now fully dry (wiped the access stain off a day or two later with the help of mineral spirits, and then let dry for a week).
My question is: is there a way to properly apply tung oil to the stained wood without removing the stain during the sanding process? Do I simply need to wait longer for it to dry, not sand between the first couple of coats, use a finer grit sandpaper, or what?
Bonus question: This being my first woodworking project, my sanding left something to be desired. There are very minor sanding marks in the wood that I didn't notice before staining. They are mostly in the same direction of the grain of the wood, but a few of the swirls I didn't match perfectly. Is there anything I can do to fix this without removing the stain and starting over? It doesn't bother me very much, but I would feel unacceptably lazy if I didn't even make an effort to fix it.