Not to pick on Home Depot's brands in particular but you've experienced one of the many problems with "off the shelf" products for homeowner use. ALL these products are packaged in a form that is inferior to commercial grade asphalt sealers. Even if there is a commercial grade sealer with the same name. They often sit on shelves for months getting from manufacturer to warehouse to retailer to you which adds to the problems. The nationally recognized standards for asphalt sealers published by the ASMA (Asphalt Sealcoat Manufacturers Association)and the PTCT (Pavement Coatings Technology Center at the University of Nevada, Reno)require graded silica sand in all sealers for wear and traction. Commercial sealers used by professional contractors are sold in a more concentrated form and must be mixed and/or applied using specialized equipment. Good manufacturers test batches regularly to insure consistent quality. These standards must be sacrificed to some extent in all "bucket" materials to produce a product with a shelf life that is "ready to use" and can be stirred and applied by a homeowner. As for the number of coats, it's like paint. Two thinner coats will perform better than one thick coat.