you still need to season it once rust has been taken off. is this serious rust or just a light covering? you will need to do some heavy scrubbing regardless with steel wool and some Bon Ami or powder cleaner. scrub away until it is GONE!

you reseason it with cooking oil and put it in the oven for about 10 mins at 300 degrees

Heat that puppy up really good and rub some cooking oil or olive oil in it an then wipe it down really good. Never ever wash your cast iron skillet with water, always wipe it down with a paper to and then lightly rub it with oli oil an then wipe it down really good.

Wash it and scrub with a Core Boy then oil and put on a burner to heat the pan to seal it.

The best information I have found about restoring, cleaning and maintaining cast iron cook ware... I found on HobbyFarms.com... It covers everything from cleaning up barn finds (or Grandma's vintage cast iron ) to removing heavy rust, and how to re-season it after you get it clean... it also has really good advice on keeping the stuff clean and usable.

First, remove the rust by scrubbing it with fine steel wool...the pan rusted because it's not properly seasoned. When the surface is rust free and smooth, pour a generous handful of salt and some oil or shortening in it, and scrub the surfaces of the pan, making sure to remove all the particles left from the steel wool. Do all surfaces of the pan if needed. Now, rinse in hot water, wipe with paper towel, and rub the entire surface of the pan with oil or shortening. Put it on a cookie sheet in a 300-350 degree oven for an hour. Let it cool. From this point, don't use soap on it, rinse immediately with hot water after use, wipe clean and make sure it's absolutely dry before storing it. My mom taught me to turn a burner on high, put the pan on it, turn off the burner to let it dry after cleaning it. Wipe the entire pan from time to time with olive or vegetable oil, and soon you'll have a glorious non stick surface better than most coated pans, and you can pass it on to your children's children.