The best oil for seasoning is flaxseed oil, which has very low smoke point. I mean you can use high smoke points oils, but you want your oil to start smoking.

I used avocado, coconut and flaxseed oils for seasoning - flaxseed is the easiest and delivered best results IMO. Plus it's nice oil for salads and some smoothies. It's not a "special" oil.

As for soap, I used it from time to time. However, why my pans are at the peak of seasoning - there is just no need to use soap.