
Completely. Slicker first, which helps break up any small knots without the pain, then through with a comb gently to find any that might have been missed. But only to find them (and to then manipulate hair for shaping), not to remove them.
One of my customers with a mini schnauzer with very fluffy hair (I suspect he may actually be part poodle and she was conned) was using the comb to pull mats out and he was getting quite aggressive with her, and by proxy with me because he thought I was going to hurt him. I got her using the slicker properly and he's much happier now. And less matted to begin with!