I came across this a while back.

A lot of hardware stores or £1 shops sell foam backed sanding blocks in various grades. I think they're designed for car body repair or DIY around the home.

The thing is, they make excellent sanding blocks for removing seams, rivets etc on models with compund curves, especially if they've worn down a bit to reduce the abrasive effect. So far I have used them on things like aircraft fuselages, ship hulls and tank gun barrels.

It's possible to keep different grades by swapping the blocks every so often and cycling them, depending upon the degree of sanding required.

This method has come in most useful on my ongoing FW200 Condor project.

I use Testors/Model Master's packs of sanding film and glue them onto sheets cut from foam egg cartons. I've glued them with rubber cement--doesn't hold long, and contact cement--holds long. Both glues allow you to bend the sanders around things.