More drywall “stuff”.
Corner bead This is a metal strip you screw or nail onto outside corners. While you can simply tape and finish the corner, the metal adds strength to protect from chipping when the corner is bumped, and gives you a straight line. Since the rounded metal bead protrudes, you also have an area to fill with compound, as with the tapered joints between drywall sheets. As you sand, the edge of the bead may show slightly. This is okay, as you can prime and paint over it. Corner bead also comes in a metal/tape version, which doesn’t require nails or screws.
As added protection, you may want to add a plastic reinforcement to the corner after you’re done sanding.
Sanding screens These screens, which look like something you’d put on your screen door, are specially made for sanding drywall. They have an advantage over sandpaper: when they get clogged, you can quickly knock out the dust. They won’t tear either.
Sanding block and extension pole The block allows you to attach paper or screen easily, and the pole lets you get at hard-to-reach spots without breaking your back. As well, you can stay far from the worst of the dust.
Scaffolding To reach high spots and ceilings, scaffolding is essential. A couple sawhorses and a couple 2×12 planks might work.
T-braces If you’re working on ceilings, build yourself one or two T-shaped supports out of 2×4″s. Make it just a little higher than the ceiling and you can jam a piece of drywall in place while you screw it to the joists.
Paintable caulking If you’re butting drywall up against existing trim, it may not be feasible to tape the joint. But just applying mud may lead to cracks down the road. Caulk these joints before painting.