I'm not crazy about staining either, and caution folks to use aniline dyes when they feel they must. In this case, the OP is asking a specific question re: protocol for staining after pore filling. While I wouldn't do it if in his shoes, it'll work ok. I do applaud his use of varnish to fill the pores first, and on second thought with thin-shell walnut the pores shouldn't be as dramatic as with black walnut and wouldn't take as much varnishing/epoxying and sanding to accomplish said filling.
I'm not a big fan of oil finishes either, but again the OP wasn't asking about the validity of that finish, so I'll refrain from criticizing.
We have to remember a couple things about Best Grade English guns and their finishes. One, they were bought, owned, and used by rich guys. Two, in the course of owning/using said guns, those guys adhered to the protocol of sending their toys back to their makers for touchup/refinishing either as injury/wear happened or as a matter of course every few years whether they needed it or not. My point is, the issues concerning gun finishes that we strive to avoid or conquer were moot to that class of men who commissioned those guns to be built. While a warm oil finish over a tastefully stained gun stock presents nightmares to we home craftsmen in terms of application (don't burn through to bare wood whatever you do) and repairs involving finish matching (not to mention water fenestration from heavy field use), the original owners of those delectable British instruments didn't give a rat's patoot- "not my problem, old chap, I like the hand rubbed oil finish, what, and if it costs me a few bob every five years to have it maintained I'll take it out of the household budget."
The other thing about those guns is: they're all really old now and their finishes have oxidized (darkened). It would be fun to ride the Wayback Machine to see what they really looked like 100 years ago.
Last edited by gnoahhh; 03/04/20.
