You want a pin brush and a comb. Fluffing is done with the comb, not a slicker brush. A slicker brush is NOT meant to be used like a regular brush, it will be damaging to the coat and if you're not careful, scratch the skin. If you want to get a slicker, get a cocker slicker and don't use it on a show coat. (if you have one)
A pin brush is used on a daily basis for keeping tangles out. The comb is used on a dry coat to fluff. There is a technique to it, I would suggest watching a grooming video on the subject.