I guess I Have found the answer my self.
Visual Specifications are dynamically updated, when af Representation Rule in the style file is updated.
In order to propagate the change in symbol to relevant featureclasses I will run the Drop Visual Specifications which removes the rep-fields related to the specific specification.
Thereafter I wil run the Calculate Visual Specifications which will re-create the relevant rep-fields, now with information from updated Visual Specifications.
Hopefully this can be done multiple times without a problem - everytime a relevant symbol needs to be modified.