DrJynx86answered grow question 4 years ago Neem won't do much with caterpillars, you need to use a product for that kind of bugs, or like you do, manually killing them one by one by hand.
I don't recommend using any chemical product, in my experience is better for the ecosystem to just kill the ones you naturally find, and let the birds close to your girls to feast on them, keeping the equilibrium and helping them thrive.
Keep on the good care!
Happy smokes!