You will need to use something like Dawn dish soap to remove the oil from the Hartz product. The good news is that it also kills feas.
Get a good flea comb - which is the same as a lice comb. Just make sure the teeth are metal and close together.
You have to treat the environment too. And repeat it in 3 weeks. Wash all of the bedding in hot water. Vaccum daily and toss the bags.
Because out house is fairly large, with lots of places for fleas to hide, we have always chosen to use flea bombs. They've gotten better over the years. We give the pets each a Capstar (from the vet) before they get in the car. We set the flea bomb and everyone leaves the house for 8 hours, with the AC/heat turned off. After 8 hours, we return to air out the house for 4 hours (all windows open, the ceiling fans and AC fan going full blast). We usually just hang out in the SUV, with a couple of movies for the DVD plays, laptops for internet and water bowls for the pets. We also treat the yard at that time.
Skin kids - Jason, Kevin, Allison
Canine kids - Bennett & Bailey (always in our hearts), Riley, Banker, Rogue and Boz
Feline kids - Zoey, Talley and Abra