I used a can of non-toxic citrus paint stripper that I got at Wal-Mart. It worked amazingly well. Sprayed it on, let it sit for an hour or so and then wiped it off (and off came all the lining). I wish I would have tried that on the drum itself....might have saved me a lot of the fun of climbing inside the barrel with the angle grinder. :clap2:
I only used it on the lid and the bottom of the barrel, but it was the dreaded red liner and it worked pretty well. (My drum contained Acai Berry Concentrate) On the can of stripper it said that it works better in warmer temperatures, so being that it was out in my garage and it was cold I stuck my shop light inside the barrel for a bit to warm the inside up before applying.