What is the best oil for seasoning blue carbon steel saute pans?

I watched a video of a chef (she had been a chef for almost 20 years) who had just learned how to keep eggs from sticking in her steel omelette pan. Cut the green tops off of several green onions and chop them up, heat the skillet up and put a little cooking oil in it & the green onions in that and stir them around to cook them. Then take the green onion outs out and wipe the pan with a paper towel. She cooked eggs in it and they didn’t stick, just swirled them around etc. like a pro chef would. It sounds like a hassle but try it once to see how it works. She said it created a chemical bond but I think it just lasts once, don’t know.