Can I drill and fill?

Drill and fill is fine, done properly

While drilling and filling is an option, we recommend a more effective approach. Instead of making holes in each cavity, consider cutting a 24" section of wallboard across the center of the wall. This method provides clear visibility both above and below the cut area, making it easier to assess the insulation needs. Additionally, you can seamlessly replace the section of wallboard once you've added the insulation, ensuring a clean and efficient repair process.