I've restored several cast iron skillets. For a real easy way to start over is put about a 1/2 cup of white vinegar in a doubled up shopping bag that'll fit your pan, double tie it, check it in a day or 2 and it'll look like it was sand blasted clean! Then cover in canola, olive, or bacon grease, wipe clean and into a preheated oven at 450*, after 30 minutes pull it out(its hot!) wipe down w/oil again put back in oven 30 min. Repeat 3-4 times turn off oven let cool. Don't use flax oil, it either pools and stays gummy, or it gets hard and flakes off!
You should've posted the whole sentence. Same article:"Nick prefers using flax seed oil for seasoning, but you can use other fats like corn, vegetable, or canola oil."I've used all types even flax, I prefer not to use it for the reasons stated. You can use whatever oil you want on your pan. I don't think anyone cares, I know I don't. People love to over-complicate things. It's vintage cookware, not really a science project.
Canola oil or rendered bacon grease works great for me!
http://www.seriouseats.com/2016/09/how-to-season-cast-iron-pans-skillets-cookware.htmlYou can read all day, but at some point experience teaches you what you need to know.