Cat owners please help

I have two very precious cats they are my baby's and my everything, one of them is 3 years old the other is alittle over 1 year old. They are not outside cats at all but somehow they have gotten fleas and a bad case of fleas at that, a week ago I bought the stuff that you put between their shoulders that's a liquid I forget the name but it's suppose to kill off the fleas and work for at least a month, well it didn't two days later fleas we're back and even worse then before. Which I know probably means there's flea eggs in the carpets an everything, so I got flea bombs so I can bomb the house but my issue is if like to bath them with a flea shampoo but I'm not sure if that'd be okay since I put that flea stuff on them before? And if it's not okay what should I do? I really don't want to dry their skin out or anything. And if so suggestions on a good flea shampoo please one that's affordable, and also my 3 year old cat has never had a bath and she's alittle jumpy as is with people holding her so any suggestions on how I cold bath her? I know she well squirm and probably try to scratch and bite me I just don't know how I can take control of the situation better so any tips would be awesome! Plus if I'm able to bath them should I buy flea collar for them? Or do you think they'd be fine after the bath?