A contractor recently restained our yellow pine wainscoting (very rustic and rough texture) and coated it with polyurethane (which we had asked he not do. Our once beautiful wainscoting is now a variation in light to very dark in different areas of our rec room. How can this be corrected and brought back to the original colour that used to match the molding and ceiling beams and upper wall wood work?
Your painter will need to use a paint and varnish stripper to remove the polyurethane and hopefully most of the stain. Since the texture is rough sanding isn't possible but it might be possible to carefully use a brass wire brush or steel wool while working with the stripper to help remove embedded stain and finish. This won't be easy but it is doable.
After the applied stain and finish is removed your painter can try to match the existing untouched wood. Note: It might not be possible to get the wainscoting back to its original color. Stripping will expose new wood that might not match the other wood accessories in your home.