A great innovation in woodworking products is the paintable and stainable wood filler. The wood filler is made with different wood species so that it will stain to shades similar to those of the surrounding wood and the filled holes will not stand out like sore thumbs. These wood fillers are spreadable with a putty knife, and when they are dry, sandable with regular sandpaper. They finish nicely and blend well with the surrounding solid wood. There are many brands to choose from and many price points to consider. Also, there are indoor- and outdoor-grade wood fillers available.
Remove paint, stain and other forms of wood finish from the surface of the wood using any combination of sandpaper, wire brushes or stripping chemicals. The wood surface should be allowed to dry completely if solvents and stripping products are used to remove existing wood finishes. Remove sawdust with a tack cloth.
Load stainable wood filler onto a putty knife and spread the stainable wood filler over the areas that need filling. Do not bother to attempt to spread the filler in a manner that will produce a finished quality to the wood surface. Apply multiple layers of filler to areas that have deep holes or cracks that require filling. Allow each layer to dry a minimum of two hours. Thin layers need to dry for 15 to 30 minutes.
Sand the wood filler and the filled surface smooth with medium-grit sandpaper (100 to 150 grit) and an electric sander. Then lightly sand the filled surface with 220-grit sandpaper. Remove any sawdust with an air compressor, and remove any residual sawdust with a tack cloth.
Apply wood stain to the prepared surface with foam brushes. Work in small areas (2 to 3 square feet) at a time. Allow the wood stain to sit on the prepared surface for a few minutes to allow it to absorb into the wood. Remove unabsorbed stain with cloth rags. Repeat until the entire prepared surface is stained.
Apply wood stain according to manufacturer's specifications. Not all wood stains are applied in the same manner.
Sanding painted surfaces may release lead-based paint into the air. Use caution and personal protective equipment when refinishing painted wood.