Definitely is killing silverfish. I have been finding various dead insects including a carpet beetle however I did find a living carpet beetle larvae crawling up a wall. This was 1 packet to 1 gallon water ratio. I am not certain if a higher ratio would work better.
To be honest. I was too afraid to try mixxing it. It is in powder form and I was afraid I might inhale some of the dust. I am giving it a rating of 4 because I used the Phantom 2 spray can( wich is very similar) and had some good results. And I know the Transport GP would be stronger. If it was in liquid form , I would be more comfortable using it.