I have no idea what the usual consensus is, but I did what the commercial
primer and then two-pot poly-urethane 2 coats. Next coat is chlorinated rubber barrier coat. After that two coats of hard antifouling in red. Then two more coats of softer more rapidly ablated antifoul for ten knot
speed in blue.
When they see the red coming through the blue they book the slip. I did the same--and I could get two years out of the outer coats of antifouling and just replaced the blue layers each time. I could probably have gotten away with just one coat of the red, but I had bought the paint
already, and it is always better on the boat
than half-used in the can.