I've read that salvaged articles and documents from the fire after the 1906 San Francisco earthquakes still smell of smoke. There are a slew of volatile chemicals including tars given off with incomplete combustion in a fire that can get embedded into every pore of wood items, and adhere to metal surfaces. These tar laden gasses can and do get into the interior of fire-resistant gun safes during a house fire, and are acidic, so should be addressed promptly.
The metal is easy because it is non-porous. A solvent wash and re-oil should clean it. Unless there is a pressing need to re-finish anyway, I would want to preserve the original finish of the stock if possible. I'd start wish a wash of all wood surfaces with a household ammonia solution which will remove any old accumulated skin or gun oils, followed by a water rinse. These oils, which will hold the smoke odors, will be turned into a water soluble soap by the ammonia. Most of the smoke particles will be removed along with the oils with this cleaning. Dry with old towels and place it into a sealed plastic bag or air tight container with a couple boxes of baking soda covering the surfaces as much as possible. Leave it in a warm place with the baking soda for a couple weeks, moving the baking soda around every couple days. Afterward, brush it off and wipe away any powder residue with a damp cloth. Repeat with a fresh box of baking soda if necessary. The newspapers or charcoal briquets mentioned by ClapperZapper will also work, but I have found baking soda to be faster, and inexpensive. Ozone generators are sometimes used to eliminate odors, but ozone is a strong oxidizer and will deteriorate organic items and cause micro-pitting of metals.
