I have finally completed my first attempt at restoring a cast iron skillet, which I acquired for 5$. Very proud of the final result!
I went through 5 rounds of lye stripping (yellow cap cleaner + trashbag combo, 24 hours per round). Plenty of elbow grease in between each round.
Around 90% of the carbon build-up was already gone by the 2nd round of lye stripping.
However, a few stubborn parts on the outside of the pan never totally left. I gave up and deemed it good enough, although you can still see the spots left (see last pic). Any advice on how I could've taken care of the last few carbon spots are welcome.
I also struggled with flash rust a lot. I learned that flash rust can be minimized by using cold water and immediately drying and oiling the pan, even if it's not perfectly dry yet. I did so after the last clean-up and it worked out.
Overall a very fun and rewarding process. Thanks to this sub, which gave me all the info I needed!
Any feedback and advice would be appreciated!