Brushing is nice, but fleas know how to run and hide in fur. Your cats are walking transport for adult fleas and shelter for their eggs. Give them a bath - nice warm water deep enough for them to sit in, lots of soap, and enough time and soap to remove both adult fleas and the dirt/eggs on the skin. Be sure every flea is washed down the drain. Do it weekly, and it'll make a difference. For yourself, if you look down and see many fleas, jump into a bathtub and wash them off with lots of soap. If you can stand it, go back to the area where the fleas were and vacuum, making mad dashes to the tub to scrub off the ones that jump on you. Wash all the cats' bedding and hang it outside for a week or more to dry. Take a critical look at the cats' lounging places - a cat tree covered with rug glued to wood or cardboard can't be washed, and will need to be sprayed heavily, for example.

My cats never learned to like a bath, but they endure, and feel much better. Be sure the water is really warm (cats' body temp is higher than ours) and there's a clean warm (hot for us) place for them dry off (clean bedding). After the summer, when the fleas have slowed reproduction a bit, is the time for the neck-dope. It's a long-term treatment, I think, and not very effective when you all are being literally eaten alive. Baths are more of a struggle when the temperatures (and dew-point in winter) are lower, so brushing may be enough most of the time.