Correcting genre etc in batches

Wondered if anyone can help me with this: I'm going through the painful process of changing/correcting genres in batches via Rekordbox. Sometimes sorting out the artist title also. Sometimes this causes the file to duplicate in iTunes? or lose the file path? Is there any easier way to do this? If so how do you go about the process? 

If I had a small music library this wouldn't be such a problem. Any help appreciated !

Thanks