If you think it seems strong, mix yours by half and see if it works. If not increase a little until it does. Or check the active ingredient permethrin on your bottle and google the amount of active ingredient on a bottle of permethrin spray for chickens. Estimate your needed amount by comparing those figures.
I bought a big light and have hung fly strips in front of the light with amazing success on catching all sizes of gnats. I prefer no chemicals if I can find an alternate way. This bug light over night has reduced the numbers of gnats. My quails are vocal again this morning which means they have gotten relief from the bugs.