I have a very large dining room table with 3 leaves. The wood is birch but has oak vineer over the wood to give it the look of oak grain. On top of that it has a thick layer of polyurathene and over the years the poly has gotten dull with some scratches and stains. I have tried to clean it but cannot seem to get the gloss back that it had when purchased. What can I do to restore this gloss without having to sand this down as the vineer is very thin and would be easily ruined if sanded. Is there something that can go over the existing poly to bring back the gloss?