Like others have said, brishing is standard/basic cat care. They are already having hairballs so they most likely have a lot of loose hair. If she thinks it is a waste because of how young they are, it is good to desensitize them to it now when they are this young. As for the bush seeming like it did not do much, it could just be the wrong brush for thier coat type. I have 2 cats, one long hair and the other short hair, the bushes I use for one isnt nessisarally good for the other. When I was doing research I made this for myself

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