TSP. You can get it at ace or lowes, Mix it a little more concentrated than the directions, use gloves! Let it sit for about an hour and rinse it off. You shouldn't have to do much sanding, if any at all. I use it all the time for furniture, because I'm lazy and don't want to strip or sand. It works great! Make sure you get in the cracks good. Actual name is trisodium phosphate. Don't use it anywhere you don't want surfaced affected, like stained concrete or any type of stone/tile that's been sealed, because when you rinse, the run off can take the finish off. Good luck!