I have an old dresser I am trying to refinish. I've already removed the shellac and am starting to sand. My question is: I can see black in the wood grain and I'm pretty sure it's mildew. Should I use denatured alcohol in case it is stain or bleach/water to remove the mildew? Regardless I know it is mildewed because it reeks of the smell.

Any help here would be appreciated!