A stiff brush?

In an inconspicuous spot, try a steam cleaning wand.

This site has some ideas:
http://www.getsmellout.com/how-to-get-smell-out-of-wood/

They rely on water-based solutions, but you can spray them on without damaging the wood. Work bottom to top.

After you get it cleaned up, prevent future odors with a coating of CLEAR shellac, the sort used in smoke clean-up. It will change the appearance slightly, and reeks of alcohol while you apply it, but it seals the wood. Or a matte polyurethane sprayed on.

Thank you lazygardens for your suggestions.

I was also thinking about getting an industrial ozone generator and shocking the rooms with ozone.

Has anyone taken this approach?

Resurrecting this convo 11 years later to add my experience and feedback. We purchased a house with a detached garage/barn that has a refinished top floor with exposed, unfinished, shiplapped pine wood walls. The previous owners had that room filled with taxidermy, so it smelled like a wet dog in a YMCA locker room. I've tried a few tactics to rid the odors, but nothing worked until I stumbled on this blog.

I was convinced the carpet might be the source, so I rented a commercial carpet shampooer and carefully cleaned every inch of the carpet. It looked 100% better but the room still smelled terrible.

Then I rented an industrial ozone generator and let that thing run for 12-18 hours at a time for multiple days in row. It sort of helped, but honestly I think it just swapped some of the old smells with the chemical-like ozone smell which was no better. I was skeptical of the ozone after everything I read online, but decided to go for it anyway. Alas, it did not even come close to solving the smell issues. Also, ozone is super toxic, so I'd say it was a net loss on my end for the effort dealing with it.

I was considering sealing off the wood with shellac, but ran across this blog and would like to share my winning solution that saved me the trouble of painting it. I mixed up a few batches of the following recipe and used a landscape pump sprayer to apply it to the wood paneling:

• 2/3 gal white vinegar
• 1/3 gal hot water
• 1/4 teaspoon lemon essential oil*
• 1/8 teaspoon peppermint essential oil*

*These oils are not optional--they really help to cut through the smell and are super effective at replacing odors.

Working in approx. 5 foot sections, spray areas of the wall one at a time. Then run a thick bristle brush across the wood, side to side. I cut a few inches off the end off an old natural bristle broom which worked perfectly and had the long handle to reach up high. One pass of the brush is fine, but this step is important as it helps to drive the vinegar solution into the wood fibers. Be sure to shake the sprayer reservoir before every application to keep the essential oils mixed up evenly. Let it dry and in a day or two your wood paneling will smell a million times better. Hope that helps!