Bathe your dog or cat in Dawn dishwashing liquid. Also you can boil some orange skins and lemon skins together, let cool, and put in a spray bottle.Spray your dog or cat daily.Here is another tip, keep your grass cut real short, also water the grass frequent.This keeps the fleas down.The sun bakes them and the water drowns them.
You have to be careful what you apply to cats. Many essential oils are extremely toxic to cats, so be careful with orange peel if want to try natural remedies.
Also, fleas thrive in a moist environment so I highly doubt that keeping your lawn wet will help at all.
I wonder what your sources are on any of this, actually.
Also some of the topical flea and tick products will also kill the existing fleas (though, if you are going to bathe the cat, do it before applying the medicine). Advantage is a good product to apply, I believe you can only get it from your vet.