yeah, while I didnt go to the extreme of Mark
mine were (2 of them) sitting in a milk crate outside (I thought under cover)
rusted to all get up

used a wire wheel to clean the most rust off
then 1kg of rock Salt & 1/2kg of cooking Salt and 1 Potato
scrub the inside using the potato as the scrubber, in the mixed Salt
(took me about 40 mins each)
rinse with water, then on the hot plate (Gas) to get it warm
rub the inside with Rice Bran Oil - has a higher burning temp - usually about 20 mins baking on the gas with the oil
once cooled - fully cleaned and seasoned Oven