We got a pine bookcase, wood puttied what needed to be, sanded, then painted with bright yellow semi gloss interior latex primer+paint. During the painting it occurred to me that priming/sealing wasn't done (it's been years since I've painted wood). Now, after four coats of paint the wood is still clearly visible, and let's not talk about the knots. Without sanding the whole thing down back to bare wood, is there any product that can be applied over the paint so we can just keep going?