Roger,
If you do the brillo and oven method, you are essentially starting from scratch. You need to season the pan like it was brand new...
You season a cast iron pan by rubbing it with a relatively thin coat of neutral oil. Use vegetable oils (canola, sunflower, etc.), shortening (like Crisco shortening) or lard for seasoning your cast iron pans.
Place the cast iron pan, upside down, in the oven, with a sheet of aluminum foil on the bottom to catch any drips. Heat the pan for 30 to 60 minutes in a 300 to 500 degree oven. Once done, let the pan cool to room temperature. Repeating this process several times is recommended as it will help create a stronger "seasoning" bond.
The oil fills the cavities and becomes entrenched in them, as well as rounding off the peaks.