When I patch tubes, I hate sanding, scraping, and shaving the tube to
get rid of mold-release, crud, and little ridges.
I recently found that a flexible sanding block, the kind used by
painters, works better than anything else that I've tried:
http://www.selleys.com.au/Rota-Cota-Sanding-Blocks/default.aspx
It's just sandpaper glued to a square-edged block of flexible foam,
about the size of a bar of soap.
The block is easier to grab and use than plain sandpaper, and the
slight flex seems to help it erase ridges.
It works so well that I'll buy a new block when the one that I stole--
Er, I'll buy a new block when the one that the painters forgot wears
out.
Cheers,
Carl Fogel