My Katie is a normal coated Pem and I got a small short coat for her and it works well tho I wish I had gotten a medium but the small also works well on my 1 cat, the other cats get a comb.  Max was a true fluffy with a long coat, as Jill said they don't work well on them at all, I also used a slicker brush on him.  Brady, our newest addition, has what they call a glamor coat.  It's longer than normal but not a fluffy, it's very thick and plush and sheds worst then a normal coat or a fluffy combined.  The furminator works great on him.  Fluffies don't shed as much as a normal coat..at least Pems don't.  You just have to watch for matts behind the ears and in their armpits and their butts if you don't keep that reasonably trimme...which also cuts down of having to clean it all the time.  Instead of leaving a corgi sized layer of fur on the carpet when they get up they tend to just have clumps that you can see and they just fall out and you can pick them up off the carpet. (insert laughing smile here)

And we need a picture of your beautiful baby!

I use a medium for my Corgis plus a 2 sided rubber brush you put your hand into. I need both because they each do a different job. I use the rubber one more but have the furminater for getting rid of the thicker coat when it starts showing and weekly cleaning.

If you're still looking, my personal choice is the "Master Grooming Tool" for my second rescue with a standard double coat--does a better job than Furminator in minimizing quantity of fur balls floating around the house. I used this on my first Fluffy rescue but gently on the shorter fur areas and as comb for leg feathers and "bunny butt" hair. If Fiona is indeed a fluffy, you might consider a beard/mustache trimmer (cordless, cheap and convenient) for her fluffy paws. (Oh. If Fiona ever picks up bubble gum in the paw-hair, try foot massage with mayo to unstick the gum.)

https://www.amazon.com/Master-Grooming-Tools-Stripping-Contoured/dp...