I use liquid Diazinon and spray it on, keeping the animals off of it until it dries (I do this in the Spring and end of Summer)...not a flea to be found. Works well for fleas, mites, millipedes etc etc.
It is important that the animals not get it on their feet/paws to later lick. It will make them sick and could be fatal if they get enough of it. Once it has dried you are fine. I would not use it if you free range and the girls can eat the grass with it on it.