Is there a tool or technique to do this?

[ian]

the motor industry has the tool you need, it's used for polishing the inside of engine cylinders. The model I've seen used was driven with an electric drill.
sorry, but I'm not sure what it's called nor the number of sizes available

[Ashore]

Your proberly talking about a flexi-hone, but its for removing metal and wouldn't be of any use here, plus their bloody expensive

[ian]

Your proberly talking about a flexi-hone, but its for removing metal and wouldn't be of any use here, plus their bloody expensive

you may be right, but the tool I recall could have been modified to work wood by glueing sand paper to the paddles.

[tea lady]

What about these bristle disks?

CWS Store - Scotchbrite Radial Bristle Discs | Carroll's Woodcraft Supplies

[dakotax3]

Laya, I've also had a look at your other thread to see your finished work as a whole. Hand or powered sanders for simple curved surfaces are not available mainstream; and forget compound curves. You'll have to really dig deep to find what you want or make your own. The smaller bobbin sanders shown earlier are typical of what's available.

The first image shows a sander a luthier modified to sand the waists of a guitar. The blue piece is a very short length of foam rod typically used as a flotation device in swimming pools and commonly called foam spaghetti. The obvious flat side enables the transfer of the orbital motion from the sander plate. In this case the opposite side is untouched but there no reason why it couldn't be re-radiused to various curves. Indeed, you could make your own curved block the full size of the sanders pad from high density foam.