Set aside suitable single serving milk bottles. Make sure you wash them out really well; old milk smells really bad. I got these bottles at Chick-Fil-A. If you don’t eat at that restaurant, ask all your friends to save them for you or find a similar bottle elsewhere. Depending on your needs, you may want to start collecting well in advance. (I’ve been known to save all year or longer for projects.)
Paint on the faces with black acrylic paint and let dry. Your kids will want to make some too! I accidently discovered that if you paint the face and let it dry a little but not all the way, you can use your brush to slide around the paint to make even scarier faces.
When your paint is dry, use a hole- punch to make two holes at the top of the bottles (see arrows in picture). Then use scrap ribbon or wire to attach your ghosts to a set of string-lights: use the holes you just made. Put one ghost over each light.