K2R, kitty litter, and corn starch all will get the fuel and exhaust out of the wood of the plane. But you have to know that it takes more than one or two applications. You are going to have to really work at it. With the K2R and corn starch you need to use your heat gun (or a hair dryer) to heat up the wood, as you heat it you will see the oil "ooze" out of the wood. Spray the K2R on the wood, or rub the corn starch in, and then wait until you see them getting soaked with the oil. Use a brush and rags to remove the K2R or cornstarch. Then repeat. How long?? Until you don't see the oil seeping out when you heat it up. Be advised this can take hours and hours worth of work, it's going to take awhile. With the kitty litter you do the same thing with heating the wood, but instead of rubbing the kitty litter onto the wood put the fuselage in a big baggy (or a trash bag) filled with the kitty litter, and make sure you get it inside the fuselage too. As with the other materials keep repeating until you get it all out. Once you have the oil as much out as you can you need to seal up the wood. If you have easy access you can fuel-proof with epoxy and heat. Use 30 minute epoxy and put a small blob of epoxy on at a time and heat it with your heat gun (or the blow dryer) until it thins out and then spread it out with an epoxy brush (acid brushes from an auto parts store), and keep doing this until you have the entire area covered. If it's inside of a fuselage and you can't get at it with the heat you can thin epoxy with alcohol to brush it on. Mix your epoxy and then add alcohol a couple of drops at a time until it's just thin enough to brush on. You don't want to get too much alcohol in it or it will never set up and remain soft. Sealing up the wood will keep any more oil from seeping out, and from any more fuel getting into the wood.

Hope this helps

Ken