I have a very soft knotty pine dining table. It is so soft you cannot even use it to write on without it indenting the wood. I am refinishing it & need to know what I can use to varnish it so that it dries hard enough to allow it to be used instead of just looked at. I have minwax superior durability polyurethane that I have experimented on another piece of wood (3 coats) & it is not hard enough. Any suggestions??