Pruning cuts should be made so that only branch tissue is removed and stem tissue is not damaged. At the point where the branch attaches to the stem, branch and stem tissues remain separate, but are contiguous. If only branch tissues are cut when pruning, the stem tissues of the tree will probably not become decayed, and the wound will seal more effectively.
To sand coves, wrap sandpaper around small lengths of clear flexible plastic tubing. Most hardware stores carry this type of tubing. Choose a diameter smaller than the radius of the cove. Slice the tube down its length and slip one edge of the sandpaper into the slit. Then wrap the sandpaper around the tube and hold it tightly.