how do i clean pillows properly?

The guides disagree because it depends what's inside. Check the label first. Polyester fill and feather/down: these usually go in the machine. Wash two at a time so the drum stays balanced, warm wash, a small amount of detergent and an extra rinse, because leftover soap is what makes them clump. The drying is the bit that takes patience - tumble on low with a couple of tennis or dryer balls, and keep going until they're properly dry right through. Damp in the middle and they'll smell within days. Memory foam or latex: never in the machine. Spot clean with a little mild detergent on a cloth, then air them out by an open window. For yellowed ones, a soak in oxygen bleach before washing helps a lot.