I just did a bathroom myself and am darn proud of it. From my experience, it's not the surface finish left by the sanding screen. I just used "medium" Norton which is about 120 I think on all coats. What is an issue are obvious dips and high spots--they will show. I missed a few shallow hammer blows and they showed up upon painting. The texture did cover where I kissed the drywall tape a little. If you can feel your joints dip or rise, they will show.