I always bathed first, and then applied Frontline last. At first I thought the Frontline wasn't working, because when the hair is dry it wicks the medication away from the skin. So I started putting it on after a bath where the damp hair was more easily parted. This technique was only used on one cat. And no, I didn't wait 24 hours before putting on Frontline, but here's why I think that method won't work anyway:
For the other (the one that I didn't bathe) I lightly dampened my fingers and parted the fur that way, and then applied the medication.
Both cats had fleas again within a couple of days. Can fleas be immune to the Frontline? I was using Revolution a couple of years ago (when I had a vet that distributed it) and I could comb through my cat's fur and see dead fleas soon after applying it. With Frontline that has never happened.