I think seasoning should be thought of as a base. You initially season raw naked cast iron so that it won't rust. Once this is done I think you should concentrate on using the piece often. It is constant and steady use that will give you a glossy smooth finish that resists sticking.
People are looking for a way to season a piece of cast iron and have it all black and slick and non-stick in 30 minutes or an afternoon. I don't think this is reasonable. The preseasoned pieces that are offered by Lodge will save you a bunch of time but they are just giving you a head start.
1) Here is the method I use on smooth (antique) pieces:
- Scrub piece with soap and very hot water.
- Turn upside down and place into an oven set at 140 degrees for 30 minutes.
- Remove from oven and coat with a very thin layer of Crisco or Lard.
- Return to oven upside down and raise temp to 250 degrees for one hour.
- After this I use the piece a lot.
- Use it as a roasting pan - roast chicken, vegetables, elk, - whatever you like.
- bake biscuits, cornbread, small pizzas, scones - cast iron is phenomenal bakeware.
- saute mushrooms, onions, shallots, peppers, celery - aromatics and root vegetables.
2) Rough finished cast iron will never get as slick as the older smooth pieces but they can be seasoned faster and they will be fairly nonstick. Some people advocate seasoning rough finished pieces (such as Camp Ovens and Fajita griddles) at 500 degrees.
This does work in applications where you aren't trying to maintain a glass smooth surface. Like with the method listed above you'll want to use very thin coats of lard or shortening. Place the coated piece (upside down) into the oven and crank the heat to 500 degrees for 1 hour. After 1 hour turn the oven off and allow the piece to cool to room temperature (several hours for big Camp Ovens).
*UPDATE* After more experimenting I still think this works well but I think you should first season the piece at 250 degrees. On two pieces I worked on recently the high temp seasoning flaked off in places once I started cooking with the DO. I've seen this before and I've concluded the high temp seasoning is a nice hard coating but it is on the brittle side. Lay down a couple layers of the 250 degree seasoning as a primer. This low temp still gets into the pores of the iron and it adheres better. After this you can crank up the heat to get a hard black coating.
3) Another option that works best for skillets is to season the piece like one seasons a wok. Get it good and hot on a burner (outdoors is best) and wipe the interior with an oil soaked wook of T-shirt or wadded up paper towels. Let the pan cool then heat it up again until literally smoking hot and wipe it down again. Repeat this process 4-5 times and you are on your way.
I've tried all kinds of oils and solid fats over the years. Lately I think I favor Crisco for the initial seasoning and a good quality Extra Virgin Olive Oil for the rest. Both have a relatively low smoke point and this is helpful when seasoning because you are trying to get the iron hot and the fat to polymerize onto the metal.
Conclusion: There is not just one way to season or "sweeten" cast iron. Consider the type of piece you are using and whether it is rough or smooth.
The worst method IMHO is the one prescribed by Lodge. 350 degrees is a lousy temperature for seasoning because it is hot enough to make the greased-up black iron sticky but not hot enough to burn the oil and begin the polymerization.
Stick with 250 as your initial temperature, then increase the heat to 450, then hotter if you can monitor everything. On smooth pieces you need to pay attention and do not crank the heat and walk away. At high temps the oil will congeal into dots and lumps in as little as 10 minutes.
For these pieces keep the high heat duration short and be ready to wipe them down with more Crisco or lard (or oil) frequently.
Please see this follow up article for another method that works well.