Counterconditioning is similar to Classical conditioning and is used to modify conditioned behaviour and often referred to as reciprocal inhibition.
Simply give your dog a treat that he/she goes crazy over every time the scary/strange object appears within your GSDs sight.
REALLY, it is that SIMPLE!
It is incredibly important to give the reward as soon as your dog sees the scary thing. Then simply repeat the process over and over again until your GSD exhibits signs of happy excitement at the sight of what was previously was frightening to them. To help you understand when your GSD is happy or fearful read about Reading Canine Body Language.
Counterconditioning example:Your dog is scared of your hair dryer. This is how we use counterconditioning to modify this behaviour.