Whether you have a brand new boat with no bottom paint or a 10 year old boat with several layers of paint, it’s worthwhile to give consideration to applying epoxy barrier coat and compatible anti-fouling paint. Epoxy barrier coat, such as Interlux Interprotect 2000, can help prevent osmotic blistering. At the very least, it provides a suitable primer for your anti-fouling. I’m not a believer in “skip sand” products or procedures. There is no substitute for properly preparing a substrate for a paint process for sanding. Sanding etches your gelcoat and allows the initial coat of primer to bite into the surface. If the first coat of a process doesn’t bite properly, neither will the succeeding coats and you’ve just thrown thousands of dollars overboard. After 30 years of applying these systems, I can determine the degree of care (or neglect) a boat bottom has received in its lifetime.