If done right, you will have something like this.

When you look at the image closely, I probably used just about four (4) shades of Gray plus white to separate my elements.As long as not one shade is similarly close to another, you're good to go.

This is how it would look when the inks are hidden.

Keep in mind to have your flats as tight as possible, for the sake of less frustrating process of selecting later on.