In a heat safe container, add 4 cups of hot water, the baking soda, and the dish soap. Lightly stir together.
Submerge your pillow cases in the mixture, and add in more hot water until completely covered. You may need to place something heavy on top, like plate, to weigh down the pillow case so that it is completely covered with water.
Set aside and let soak overnight.
The next morning, rinse out the pillow cases with cool water.
Wash using a small amount (depending on how many you are washing) of your regular laundry detergent and 1-2 cups of white vinegar.
Dry outside in the sun, if possible.