I have an old cast iron skillet which has been with me for over 40
years. It has become quite well seasoned over the years. I usually
use very mild liquid dish soap, and a nylon scrubbie to clean it up. I
wipe clean with a terry towel.

If it begins to want to stick a bit. . .I will rub it down on the
inside with vegetable oil, and place it in a low temperature oven for a
few minutes to season.

Myrl Jeffcoat
http://www.myrljeffcoat.com