The article outlines the steps to bulk update custom field values using the custom field maintenance tool.
FOLLOW STEPS BELOW:
1. Within the Sync homepage, select Tools and then Custom Fields
2. Select the type of custom field that you are wanting to bulk update
3. Filter to the job/product/documents that you are wanting to update
4. Select all the options you want to update
5. Set the custom field value that you will be updating
6. Select 'Update'
NB. For a quick tutorial watch below