We recommend 120-grit or 150-grit paper for the best ... The edges of the box can rip your sandpaper, or a piece of the paper facing on the drywall can roll up under the sander and tear off.

Here are the two grit progressions we recommend: 80/120/220 and 100/150/220. It's tempting ... You can buy small rolls of adhesive-backed sandpaper at home centers and woodworking supply stores.