Newfs should have a double water resistant coat. That coat should NOT be shaved.
Mother nature presents the dog with insulation in the summer and in the winter.
Brush your dog weekly if possible. It is easiest to teach your dog to be brushed on a grooming table. Stand your Newfy on the grooming table and you will find it much easier on your back to brush, blow dry, do toenails and trimming, etc. Do remember also to teach it to have its tummy brushed by having it lie down on the floor. The Newf has hair which is short and fine right on the bottom half of its ears, but the top half, if left untended, will grow right down over the bottom of the ears and cover them over, making your Newfs ears look more like a Spaniel's ears than a Newf.