Prefilling is an essential step in drywall finishing, especially for filling in large gaps or damaged areas. By using a product like Easy Sand, you create a strong backing for your tape and mud, leading to a smoother and more durable finish. Not prefilling can result in tape twisting, difficulty in coating, and ultimately a less professional-looking result. While not everything needs to be prefilled, it is a crucial step for ensuring a better finish, saving time in the long run, and preventing issues with cracking or shrinking. So, make sure to prefill where necessary to achieve the best results in your drywall projects.