All those suggestions are good. One more thing you can do that may help, and doesn't cost a thing except time:

Take some time to examine your floors VERY closely and VERY carefully, and you will learn to identify the flea egg cocoons that are doubtless there. Once you do, take the time to scrape them loose (thereby killing them) and vacuum them up, and you should dramatically slow down the hatching of new fleas. This will help you get in control of the situation much faster.

We also have hardwood floors, but one year we still had an infestation of fleas that just would not quit! I finally discovered that in the grooves between the boards, the flea cocoons were lined up just waiting to hatch. They are white and look like small grains of rice. They attach themselves to the wood and a vacuum will not pull them loose. It is necessary to take a sharp tool to smash them and drag them out. A table knife will work, or a letter opener is good, too.

You will doubtless find, as I did, that the with activity in the house, the eggs that fall off your dog get brushed to the side where they spin their cocoons and attach to the floor. Typical places to look are under the sofa, under tables, and around the perimeter of the room -- especially up close to the baseboards.

I have a home organ with full pedal board, and once when I pulled the pedals away, I was shocked to see flea cocoons lined up between all the hardwood boards in the floor. Then I knew why all my vacuuming and dog washing had been for naught! Since learning where to look for the flea cocoons and destroy them, I've had no more infestations.

Hope this helps!

Dottie