I plan to do something like this on the inside surfaces. Somewhere along the way I read about using an innertube cut into a circle around the valve stem which you insert into your drill chuck. I tried it on my Guillemot Coastal concave bow and stern with a six inch diameter circle of innertube and an eight inch diameter piece of 80 grit glued on with contact cement. The variable speed drill offers plenty of speed control. The flexibility of the rubber plus the extra inch of paper extending beyond it offers plent of forgiveness. The rubber conforms perfectly to any surface I put it to at any speed. The down side is that I used it up near the cockpit and caught the paper on an edge when I increased the angle too much... no damage to the boat but tore the paper, and I was done with the important areas anyway so it really wasn't bad.

For the next go I bought some emerycloth backed sandpaper but I haven't used it yet.

Below is text (and picture I hope) from Oneoceankayaks.com. Valclav writes:
Transforming the hollow into a smooth and fair surface with a disk sander.

The 7" 36 grit paper is intentionally larger than the 6" rubber disk. The large paper is far less likely to sand grooves into the wood because there is no pressure on the edge!
You can also sand different radii hollows by tilting the disk to the side. There is NO better tool for this job. If you don't have a disk sander, do it with an orbital sander (60 grit) or by hand. Planes will not work here.