I added tea tree oil to the dog's shampoo and spend a good long time soaping them up. Dripping a little water on them, more sudsing. We're having an issue, but this is killing adult fleas. They are dropping off with lots of liberal soaping, and then lots of water to rinse.. Some hang on for dear life.
After a bath I look at stomach and genitals. I've found a few no longer living fleas trapped there.
A lot of spot on treatments are less and less effective as said..
You may also have to treat your house repeatedly. Eggs and flea dirt fall off your pet, what you see on them is only a tiny representation of what they've been up to. Stats are like 50-80 eggs a day per flea (ewwww). In the pupae stage they are apparently impervious to insecticides and sprays, DE should still work though.
Also, sadly don't think the worst is over and become complacent. You may have just killed the current fleas. More may hatch even with sprays and vacuuming. Ours was improving, college was kicking my @ss.. and now I have issues again. I need to vacuum more often and be checking the dogs daily for dirt signs and bathing them if I find any.
I gave up and ordered some capstar yesterday. Sadly, being Canadian decent flea stuff shouldn't be Rx, but it is. So I have a 8-10 day shipping wait for it to get here.