Greasy cast iron pan

Scrape off what you can. Put it in a self-cleaning oven for 2 hours. All the residue will turn to powder that you can vacumn off. Reseason a few times and then use it. I never know when buying an old cast iron pan what it was used for and prefer this method. Then I know my grease is my own.

Don't touch it! That build up is what makes cast iron cookware so good. Wash it like you do your other pans and put it away. It'll be the best skillet in your pantry....Dennis

Try this. I've done a bunch of skillets this way.
www.wag-society.org/cleaning.php I use the electrolysis method.

Use it!
Cast iron pans work best if they have a good layer of oil buildup on it. If your really want to start over have it media blasted and then start over seasoning properly. But ill guarantee if you use it at all it will look like it does now in a year or so.