The most popular mushroom knives on the market come with a brush. It is almost a standard in this industry, yet you can also find knives without one. However, you will have to find a way to clean dirt and soil when you pick mushrooms. If you get a knife without a brush, chances are you will need to purchase a brush separately. In other words, it pays off getting everything in one package. Since the brush is usually attached to the handle, you are less likely to lose it.