My Bogie is a cotton coated Biewer, I had a horrible time keeping the hair under his arms and his belly mat free. If you are going to keep Wallee in a full coat, you can shave the hair in the arm pits where it mats so badly and also the belly. You cannot tell it is shaved unless you lay him on his back.
I gave up after almost 2 years of constant brushing and combing to keep Bogie's mats out of his coat. I now keep the face and leg hair long and shave him everywhere else. It works for us year round. I keep shirts on him almost all of the time and he looks like he has long hair all over when he is dressed. He is much happier without all the time consuming grooming...and so am I