I've used the same two Griswold skillets (almost daily) since 1989 when my grandma died. I think that one of the problems that people experience when trying to season iron is that they think that they need to build up a coating or a layer of something on the surface. Seasoning is mostly filling in the pores and leveling out the surface. I've seen rough-ass Lodges that eggs would not stick to because they were seasoned correctly and I've seen near-mirror polished skillets where the eggs stuck on contact.

They key to a successful season seems to be very light coats of a high temp oil and multiple heat/cool cycles. The real seasoning occurs after a few frying sessions.

We always used lard or crisco for our annual season after burning off last year's seasoning.

Last year I tried canola oil and it did a nice job.