I would never use Easy-Off on cast iron. Who thinks this is a good idea?
If your old pan needs to be rejuvenated use a little olive oil and a synthetic wool pad. It takes some elbow grease if your pan is really nasty/rusty, but it gets the pan back to where it can be seasoned.
Seasoning is simple. Some oil and heat... repeat a few of times. Those instructions can be Googled.