my wife wants me to take out the bathroom wallpaper, and paint. Ok, but the wall under the first strip I've removed has a residue of uneven (what I take to be) sizing, a tiny grid-like pattern. Hence, the paint would not look smooth. Is this sizing, and if so, are my only choices to skimcoat it with drywall mud, or somehow remove it? Can/should it be sanded off to smooth? Or would paint in fact dry to a smooth surface without dealing with the "grid"?