I have the same problem every year mate, they are a pain, not only do they damage the feathers they stop the birds relaxing properly at night !!
I always used Vapona years ago, but like most things that actually worked, you can't get it any more.
We have other members who are having trouble with them too, one of them said to buy a small spray mist can, get some of the Johnsons lice and mite spray and just spray the loft with it. I tried this, I only used it almost like you would an air freshener, I did it at dusk with the birds in the loft, obviously careful not to spray too much directly into the birds faces, a couple of times and I have to say the results were amazing, I've barely seen a moth since !!
https://www.amazon.co.uk/Johnsons-Anti- ... 72d4687232