I've never used any soap to clean my Lodge skillet. I scrape up any stuck food with a flat spatula, then scrub it with a wet, plastic pot scrubber and rinse it out. After that, I coat the inside with Crisco and put it on a burner until it just starts to smoke, then turn off the burner. I'll come back 10 minutes later and wipe out the excess Crisco and it'll be good to go for the next round of cooking. The point of cleaning it this way is to let the Crisco carbonize and coat the cooking surface a little bit more each time.

Our grandma's skillets were so good because they've been cooked on & cleaned this way for 50 years or so. Also, the older skillets had a smoother cooking surface to begin with. The new Lodge skillets are sandblasted or something during the manufacturing process and that gives them a rough, slightly pebbly cooking surface when you first get one.