Easiest way to wash a pillow?

Check the tag first. Most polyester and down pillows are fine in the machine: two at a time so the drum stays balanced, gentle cycle, a little detergent and an extra rinse. The drying is where people go wrong. Low heat, a couple of tennis balls or dryer balls in with them, and keep going until they're properly dry all the way through, which takes longer than you expect. A damp middle goes musty in days. Memory foam is the exception, don't put it in the washer. Wash the cover and spot clean the foam.