I am a lab breeder, and I have 4 adult dogs. Not only do all 4 of my dogs love to get brushed with the Furminator, but I give one to each person who buys a pup from me! I see a big difference in the amount of hair around my home when we use the Furminator regularly.
I am up to six labs now and use the furminator on all. I would recomend the large size. I have owned both the short hair and long hair versions. Both work fine. The long hair version seems to be able to take more srtikes before needing to remove the accumulated hair.
I've got 2 lab mixes and bought the medium/short hair version. The puppy boy has the longer hair so he was the one I mostly bought it for and it seems to be the right size. Compared to the other brush we have (wired bristles with tiny beads on their end) he loves it and is real good when I brush him, as long as I do it when he's not in a playful mood:) I don't get big clumps of hair out but rather, smaller ones and I just pull it out before a lot gets of hair, and do that a few times. It seems to do best around his neck and on his back near the tail. I find it works best if you use one hand to secure the skin and pull down w/ the tool in the other hand. Do it on an angle (so inside of teeth are closest to skin) but DO NOT press. By holding the skin and dragging the brush, it will pull the hair out more efficiently. I would recommend shorter strokes. The other dog is female and has very short hair (not as big a shedder). I have to be very careful with her because her skin is extremely sensitive. My strokes are very light with her. Again, she's thicker around her neck so holding the skin around that area with one hand and pulling with the other is still okay. She is very good with it and no bumps have developed. I will also add that I bought the Fuminator shampoo at the same time I bought this. I've only used it once so I can't be sure it cuts down even more on the shedding but it does smell very good and the dogs seemed to smell good a little longer then usual. The female didn't have a reaction to it either so that was another plus as there was only one other shampoo we could use on her before now.