Using Data Sync it's pretty easy to apply bulk updates to meta data stored in your Active Directory. One way is to export the whole AD to an Excel Spread sheet then sync changes from the Excel Sheet back to the AD.
However another way if you just want to apply a transformation is to use Dynamic Columns, here were updating the Company Name and Email Address fields of all our Users in the AD. We set up a project that has the Source and Destination set to the same data source and we use Dynamic Columns to calculate the changes we need.
Simple Dynamic Columns like this apply the Transformations we need and all we need do is Map the new Dynamic Columns to the AD Fields.
The completed project in Data Sync