Smooth Durabak should be sprayed on or brushed, not rolled. If you spray it, you need a large (1/4-inch-diameter) sprayer tip and the Durabak needs to be thinned with 10 percent xylene in order to flow through the spray gun. If you brush it, you need a brush with a specific nap. We had neither, so we brushed it on with a too-coarse brush and hoped that the laws of physics and chemistry would be temporarily suspended. They weren't, and we ended up with a coat that was full of runs and sags. Despite our less-than-ideal application method, the Durabak dried to a super-tough protective coat that’s water and abrasion resistant and is easily repairable should a touch-up be required. We've got enough smooth Durabak left over to try applying it the right way next time.