When you spray the brood combs, you end up spraying a lot of bees. Luckily that doesn’t seem to kill the bees. It didn't in my case at least. Unfortunately it also doesn’t seem to kill the wax moths either. They are usually tunneling under the cells and under the pollen where the BT spray doesn’t get to them.
You can try the BT, but I believe you should also pull all the frames that the bees can’t cover and freeze them. Pay extra close attention to the pollen frames, the wax moths LOVE those frames. Replace removed frames with plastic foundation. Luckily the wax moths can’t eat plastic. Add back in the old combs over time as the population grows. Once the weather gets cold, the wax moths should go into hibernation and you can add back in the rest of your frames at that time.