Fuel soaked balsa;

There is a product that may be hard to find now days due to its health hazard. The product is called K2R, try and find this in your local grocery store and if it can't be found then get some sort of powder like talcum powder sprinkle this on and let set over night wipe off and do another application. After that is done then get a strong heating gun hence "harbor freight" has one. Then heat the wood this will draw whats left in the wood to the top then use a paper towel to wipe it up with.

Randy