I got this cast iron from my grandma...it was outside, but in a pole barn for at least the last 12 years.
Some of it is Griswold and I don't want to destroy its value. Any suggestions.
Wash with hot soapy water and a gentle brush to remove the surface rust. Then season as described above. After one hour, turn off the oven and allow to cool with the oven door shut.
....and some rin up hill and down dale, knapping the chucky stanes to pieces wi' hammers, like sae mony road-makers run daft - they say it is to see how the warld was made! Saint Ronan's Well - Sir Walter Scott, Bart. (1824)
I second the sandblast but hesitate on the cherokot. I restored several that was in my fathers shop. Blast, wash, dry and I season with hog lard at 400 degrees for 45 minutes. Cool wipe out, repeat 3 or 4 times.