I clean my cast iron pans with a small pot scrubbing broom that I got from a small company called Sistercraft. The potscrubber is tough enough to grind off scrambled eggs, but doesn't strip the seasoning. No salt or especially no soap is needed. I just use hot water plus the scrubber. If the food is particularly stuck on, I just let it soak for a few minutes first, but the potscrubber always does the trick better than a sponge or plastic dish brush. (And of course no steel wool because that not only strips the seasoning but damages the surface of the pan.)
Here are some photos of my potscrubber, used almost every day for 18 months and still going:


And my favorite pan:

The key to keeping it looking nice and functional is to hang it up after each use so it drips dry. That way it stays stiff for the next use. This chicken does the trick because it is right above the kitchen sink!

Here is the link to the potscrubber on Sistercraft's Etsy shop:
https://www.etsy.com/listing/251937291/trumbull-potscrubber-handmade-by
What else is everyone using to clean their cast iron pans? Does anyone else use a potscrubber broom? Post up your weapon of choice.