This prop is easy to throw together and the cost is comparatively low for the effect. Here's your parts list:
4 feet PVC (I used 1/2" instead of the usual 3/4". I feel the less PVC to fill the more air that goes to the whips)
1/2" PVC end caps x 2
2 Way Solenoid Valve (Mine is a Monster Guts)
Push Quick Male Connector
Super Strong Quick Setting Epoxy from Harbor Freight
Soft tubing and connectors - about 14" (I acquired some tubing from my work that was discarded)
Of course, flat black spray paint
Pros: Low cost, fun effect, easy to construct
Cons: Takes a lot of air! You will not be able to run this prop with a pancake compressor.
Ideally, this prop would be mounted on the backside of a wall panel with the whips coming through the patron side. My walk-through won't happen until next year so I'm putting this prop in a coffin with a dead body and rat sounds.