Hi Rich...
It may depend on fresh vs brackish vs salt water.
I race on Barnegat Bay, which is brackish, and I use VC Offshore. It's a hard vinyl paint that burnishes to a 400+ finish. And yes, barrier coats are a must. Both Pettitt and Interlux have barrier coat products (Pettitt Protect and Inter-Protect 2000E) and they come in white and gray so you can alternate colors for future sanding purposes. They recommend at least three barrier coats, but my Ensign has 5 to 7 barrier coats underneath the VC.
Three coats of VC are applied and for max smoothing, the last coat is sanded until the finish is uniformly smooth. Then, the bottom is burnished for the final finish.
Most peeps I know that race in fresh water use VC 17, but every Ensign needs barrier coats for proper protection.
Bud Brown
#1085