A piece of old tee shirt with some ordinary engine oil is fine for rubbing over the steel parts. Don't use too much oil ever! It will soak into the wood and weaken it badly. Under normal storage conditions, once every 6 months or so is fine. A lightly oiled patch through the bore is a good storage precaution but it MUST be wiped out with a dry patch before shooting, both to remove the oil and also the thin layer of dust that will have settled in the muzzle. Oil in the bore will bulge the barrel, and dust will knacker the rifling in the muzzle in just a few shots.
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