No sweat
Light sand...I've done heavy sand, lol. My USGI stock only had a "P" and an RIA cartouche. But it did have some smash marks that I thought were splinter factories and I started with 80 grit, finished up with 400 and then scotchbrite. But I taped over the cartouches I had first, and stayed away from crisp edges. I also steamed out some dents. I had nothing to lose on my stock- it was one ugly piece of wood when I started so i figured, what the hey
I'd suggest pure tung oil or boiled linseed oil instead of varnish though. That's all that is on mine. I wish I'd taken a 'before' photo. It looked like Godzilla had it stuck in his colon since 1950.
This...is maybe 30 coats of boiled linseed oil? I've lost count. Also a few coats of "lin-speed' oil.
It gets compliments at the range, which is cool, but I shot myself in the proverbial foot- it's so pretty I'm afraid to lay it on the shooting bench for fear of marring the pretty finish. I outsmarted myself once again!
It was this color after sanding and cleaning; still had the HRA trigger group and late sight:
I did a few other USGI walnut stocks and some turned a beautiful red-gold-brown when oiled the first time, some stayed pretty light until four or five coats. I've tried staining too but I don't think it did a damn thing but make a mess, lol
This is my dad's M1 carbine stock. When I cleaned it with odorless mineral spirits, it was white as a bone. One single coat of boiled linseed oil did this:
I guess it depends on the piece of wood what you'll get