"bin" from zinsser will help you
Without seeing what you are describing is hard to choose a road to lead you. How big of an area? You may want to replace a section with new. May want to 220 and re-poly. Hard to tell, need more info.I looked at some finished stained trim today where the house had water damage from a roof leak. It left the trim with water stains. Any advice on getting the stains out and making it look good again?