I wash my cast iron with normal dish soap and steel wool, and if I'm too lazy, I put it in the dishwasher. I've been doing this for 20 years. I don't "season" it. It's a pan, no more, no less. The main advantage is that you don't need to worry about scratching the shit out of it.
Needs a tiny little bit more fat than a non-stick if you want to make an omelette.
Yeah, soap doesn't hurt a fucking thing, If I just cooked with a seed oil or bacon or something I'd be inclined just to let it burn off, But if I cooked noodles or pasta or garlic or anything fragrant on there, I'd soap and scrub the piss out of it. I just make sure to throw it back on the fire and get it past 212 if it's been wet.