I have a small cast iron skillet that had a sticky surface in part of the bottom. I made a big fire in my barrel and got the pan warm, hung over the top of the barrel on a strip of rebar.
Once the pan was hot enough not to crack, I put it down into the coals for about an hour. I watched as the gunk burned off.
After about an hour, I hung it across the top again to start the cool down process.
I will brush it down and reseason it tomorrow. IT should be smooth enough to make cornbread in it again, without the bread sticking.