The instructions I received (through my trainer classes) is that the first time you use bitter apple, before spraying it on OBJECTS that you don't want chewed, you should first spray just a LITTLE into your dog's MOUTH so he develops an aversive taste to it. This way he will avoid it each time he encounters it on an object, he will remember how awful it tastes and not chew that object.
It also comes in a water based spray called Bitter Break which lasts a little longer than the alcohol based Bitter Apple. You need to apply it to objects EVERY DAY because it evaporates and loses its taste on things.
There is also a bitter apple paste which can be used on wires, etc., which lasts somewhat longer after application than the sprays.
Hope this helps clarify.
I never used it, and always "redirected" my boxers' to proper things to chew on (toys, bones, etc.) whenever they are about to chew something they shouldn't. This has worked marvelously for me and there is no need for bitter sprays or pastes. One must remember that chewing is a NATURAL activity for a dog and you will have more difficulty with Natural activities in terms of behavior modification. It takes more time and you don't want to completely deter the dog from chewing or he may become adverse to chewing ANYTHING, such as bones (which are good for cleaning teeth, etc.), or even kibble. So, I therefore recommend a good "redirect" theory of rewards for your dog's chewing rather than repellants such as bitter sprays.
Also, dogs are less inclined to chew and be destructive the more exercise they have and the more toy options they have to chewing improper things. And during the puppy/teething periods, you'll need to watch your dog very carefully to make sure he's not chewing the wrong things. You cannot eliminate ALL chewing, but you can help your dog understand what is appropriate to chew and what isn't.
Hope this helps you out and, good luck.
