Put the gloves on, set cast iron pan in garbage bag, spray an even coat of oven cleaner over the whole cast iron, tie up garbage bag (make sure to seal tightly), set aside & forget it for at least 2 days. On day 3, open the bag, wipe off all the old gunk, then repeat the process. Continue this process until all of the gunk is off the cast iron pan. (there may still be rust).
Second step: white distilled vinegar, scrub pads or steel wool, water
Third step: lard (store bought, home made, crisco, olive oil), paper towels, & oven.
So now you have a brand new clean cast iron pan. Stick it upside down in a low temp oven (say 200-250) for at least 15 minutes, pull out & blot off all "dampness", then put it back in the oven & turn it up to 500. Let the cast iron bake for 45 minutes. While it is still hot, pull pan out of the oven & reseason.