It is very normal for a dog to scratch up to 2 couple of days after a groom. It can be for a few reasons. First, anal expression, loosens the glands after expression causing an itching sensation. Haircuts cause tiny particle hairs to sometimes lodge in skin causing irritation, brush dog to help remove more of the loose hairs. The shampoo was new to your dog causing the skin to feel dryer than normal, again brushing your dog will restore the skin’s oils assisting with your pet’s relief. These irritants are common and the itching is typical for up to a couple of days after the grooms.