Fill a sink with hot water and 2 tbsp. liquid dish soap. Place the pan and the grill into the water and leave them to soak overnight.
Remove the grill pan from the sink and empty the water. Mix 4 tbsp. salt with enough water to form a paste. Scoop a portion of the paste onto a damp cloth.
Rub the paste over the crusted and burnt food particles in the pan and over the grill section. Make additional paste if needed to scrub the entire pan and grill. Use medium force as you rub to dislodge the fragments from the pan and grill's surface.
Fill the sink with hot water and 2 tbsp. dish soap. Place the pan and grill into the water and scrub them with a scrub brush to remove the food particles and grease.
Rinse the pan and grill with hot water and dry them with a clean cloth.
Pour 3 to 4 tbsp. cooking oil onto a paper towel. Rub the paper towel over the pan and grill, coating all surfaces evenly. Apply additional oil if needed to cover the entire pan and grill.
Set the oven temperature at 200 degrees F. Set the grill pan into the oven and leave it for 20 to 30 minutes to reseason it. Remove it from the oven and wipe any excess oil from the grill pan with a clean paper towel.