Clean the area to be filled with a cloth, soap and water. Wipe it clean and let it dry completely. Oil, grease and dirt can interfere with the drying of the putty.
Use a pocket knife to cut out any burned pieces around the area to be filled. If you are filling in a burned area, make sure to remove all blackened pieces of wood. Burned wood can interfere with the drying process of the putty. After removing the area, clean the spot with a cloth dabbed in rubbing alcohol. Let it dry.
Use a putty knife to apply the putty into the area to be filled. Apply the putty in a 1/4 inch layer with even, smooth strokes. Do not let the putty build up. Thicker layers will take a long time to dry and will not set as well.
Turn on a hairdryer and set it to cool. Hold the hair dryer at least six inches from the putty, moving it back and forth to aid drying. The putty can take 30 to 60 minutes to dry. Once the layer is dry, apply another layer, following the same steps.