Place them when the skunk is out foraging at night. Scattered moth balls may achieve the same effect. Keep a light on at the den site. A flashlight or portable lamp shining for a day or two will usually deter the skunk, as will a portable radio set on a news channel. The sound of human voices will keep them away.
Skunk spray is oil based.
The odor will cling and linger. Inanimate objects that have been sprayed can be washed with a bleach water solution. For pets and people, vinegar and water baths will help, as will several enzymatic odor control products available at pet supply stores or though veterinarians. Time and fresh air also will eventually cause the odor to completely dissipate. The key is not to anger the skunk so much that he feels he must spray.