Dirty Cast Iron Pans + Eggshells = ....

For some reason I have extra energy this afternoon and Bubba is content to sit in his chair and watch so I'm taking advantage of it! I've got bread baking, beans cooking, my dishes are (almost) caught up and I'm gonna spend some time shining my cast iron pans!
Those of you who follow me on Facebook might remember me posting this photo a few years back but I thought I'd share it again with complete instructions. This is one of my favorite LifeHacks, I do most of my cooking with Cast Iron and if you know many people who use cast iron you'll know we don't like to use soap unless absolutely necessary, as soap would remove the "cure" on the pan.
So that means we need to get creative with our cleaning! This is the easiest way I've found to clean my pans.

I save my eggshells; first I wash the eggwhite off under the tap, sometimes I strip the membrane from the inside of the shell sometimes I don't, the only difference it makes is that the shell is more fragile without it. If you're going to store the shells for future use make sure they're completely dry (I may or may not have had to throw away moldy egg shells that weren't dried properly) if you're using them right away just dry them for an hour or so, until they're not sticky.

Scrape as much gunk out of the pan as possible, just like you would for normal washing. Put enough hot water in the pan to cover the bottom. Take 1 to 2 complete shells and crush them in the pan. Take your wet rag or sponge, capture some of the shell and use it to scrub the pan.
Once the pan is satisfactorily cleaned, toss the shells, rinse and dry the pan and give it a light coating of oil and you're done!

What's your favorite kitchen cleaning tip?