I have created a project in IDE to migrate data from sandbox to ide delete unused components and deploy to server. This provides data cleansing to the instances. As I have selected custom labels to add in the project I get an error Java.lang.nullpointexception another error explaining custom object type cannot be cast to component type.please explain a better way to complete this in IDE with all the metadata and components gets upgraded and I can delete from ide before deploying to server.im not sure if it this process  hard deletes the unused or leftover components or if there is any other process to clean unused data please explain!

i have also tried ant migration tool initially overcame with installation problems of ant and now im confused with the folders codepkg,mypkg,unpackaged each of the folder has package.xml so I need to understand in which package's folder should I enter the complete list of components and metadata in package.xml file. This is large amount of data do I need to enter manually in one package.xml file as there is one build.properties file.and one more question with login credentials in build.properties if I want to retrieve metadata &components from sandbox and then delete unused data using destructive changes.xml  in removecodepkg folder and then deploy to production can I enter multiple login credentials in build.properties  for sandbox and  prod to retrieve and deploy.
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