I had a situation like yours - iron is not as porous as you think. It's just the surface you have to deal with. Use Dawn or another soap that attacks fats, oils, etc. and suds it up; wash well in warm water using a 3 M scrubber. Rinse, dry. You do NOT want to put this in your oven before washing.
Then put it in the oven cleaning cycle upside down. Allow to cool completely before removing. Use canola, lard or coconut oil for seasoning and then warm gently in 350 oven right side up for an hour. It'll be good to use after that