Season all of the inside, lid included, the "seasoning" will prevent rust.
Any way you can to heat, then "season" it with whatever you choose.
What happens is as it it heated, the pores in the cast iron open up.
Then you rub down with whatever grease you're going to use.
Then as it cools, it actually draws that oil/grease into the cast iron.
This needs to be done several times.
Rust will kill a dutch oven.
Another good way to season one, and help in the learning process.
Buy a can of Jumbo buscuits from the grocery store.(only 5 or 6 biscuits to a can).
Pre heat the oven and lid, then drop in 1/2 stick butter and melt it.
Open the biscuits and coat both sides in melted butter in bottom of oven.
Just flip them all over once so that they are coated on both sides.
Rub biscuits up sides of oven and inside of lid to get oil there as well.
Pack the biscuits in the bottom, no need to spread them out, they will rise up.
Then cook the biscuits in it.
A can of these biscuits is around a dollar and a great way to learn how much heat (coals) are needed for top and bottom.
Plus, you have now seasoned the oven again.
I've done as many as 3 or 4 sets like this in a day just to play with it.
Easy cheap way to figure it out.
