Aggressive resin solvent
Wear Gloves.
Returning is impossible
Resin does not just harden, it polymerizes into shape from monomers in a chemical reaction. That means to break it down, you need to destroy the whole chemistry. There is no solvent that can simply reverse it.
Wiping is easy
As long as the rein is still liquid, you can wipe it off. Then clean the parts with Isopropylic alcohol.
Manual work
Destroying Resin-Polymers is incredibly hard for most solvents. The most simple solution is usually oddly enough to use physical force. Resins are super brittle and chip off, but might damage the paint coat in the worst case.
Thermal shock
If you can, you might put your printer in a cold environment and see the resin gaining cracks, as it shrinks slower and less than the metal. Then, putting it back into the heat adds more.