My enameled cast iron was leaving sharp little blue flakes around, so I decided it was time to take off the enamel. I tried a brass drill brush first, which only dislodged the loosest flakes. Then I got the cheapest Harbor Freight needle scaler ($40), and it worked great.
My small compressor couldn't really keep up, but working 30s at a time gave me time to grab the drill brush and clean up the exposed iron.
Washed, dried, seasoned, and ready for use. (I didn't bother with the lid, which isn't in as bad shape.)
How long did this take?
A few hours, would've been faster with a bigger compressor.