Here's my new favourite tool for sanding the planking between the ribs. I's a flap and brush sander that fits onto a drill. Different grits are available. I bought this one from Lee Valley.
The new tool in use. It makes dust. Lots and lots of dust.
As you can see, lots of dust. This is Travis, my intern, discovering the joys of this kind of work. trust me, I was dusty, too.