On Wed, 15 Nov 2017 16:26:57 +0000, Rob Morley wrote:

Have you tried whacking the outside where the resin is with a rubber
hammer? That might be enough to get it to flake off without causing
much damage.

This is a method I have heard of: Place abrasive in tank, 30%--50% full. Use
grit 1-2mm, Spax screws, broken glass, ... plus 0.5 - 1 liter petroleum. Wedge
tank in cement mixer with pillows. Let run 30 to 90 minutes.


https://youtu.be/aJuGLHToRGs

https://youtu.be/zxBWcxCdNWw

Thomas Prufer