FYI on How to bulk add label, thought I will save some of your time in figuring it out if you are already not aware of it
Step 1.
Create a filter like this, could be different status for your project.
project = "Project Name" AND issuetype in (Bug, anyother status) AND STATUS in (Dev, QA, "TO DO", "In Progress" or anyother status)
Step 2.
Click on Tools on top right corner of the page
Click Bulk change all xx Issues
Step 3.
Click on the top Checkbox to Select All
Click Next
Step 4.
Click Edit Issues
Step 5.
Go to Change Labels
Enter “New Label”
Step 6.
Click Confirm button