This can be a touchy subject. The old saying (not my saying, just an old saying) “Loan out your car, loan out your wife, but never loan out your cast iron” says it all.
I'm a collector of old cast iron, mostly Griswold and have done a lot of seasoning. I will only give three thoughts here though.
1) What Glen said: “Go to lodge.com and read what they say" Note:
They recommend solid vegetable oil for seasoning.
2) For those that have not bought yet. Buy Lodge brand - they are now preseasoned and are a USA made product. Lodge is substantially better than the other brands.
3) Seasoning is like painting
, several thin coats are better than trying to apply a lot at one time. If you put it on too thick and it pools, you may never get an even coat.
Here is a picture of one of my pieces of cast-iron. This one is a Griswold Tite-Top Dutch Oven from the 40's.