Furminator? Grooming a cat with a Double Coat?

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I have a cat who has a double coat and sheds so much hair, I have tried using a standard slicker brush on her however it hasn't made a difference to how much hair she sheds. I have been reading about Furminator's and they seem like a good option however I am worried that it will cause her to be less fluffy.
Has anyone had any experience with the furminator product or do you have a suggestion as to how I can groom her more effectively to reduce the amount she sheds...

Thanks in advance.