I've always used white vinegar. After you see him chewing/biting on a surface, wet a cloth or paper towel with vinegar and wipe the surface. I guarantee the smell alone will make him run for cover. Mine freak out when they smell vinegar now, and run the other way. Don't forget to substitute a chew toy in his mouth as soon as possible after you catch him biting the wrong thing. It worked for us. Good luck.
