bottom paint

In 2003 when my boat was commissioned by gratitude marina IP did not suggest a barrier coat because the boat was built with a different resin below the water line. Gratitude sanded the bottom and applied paint. Over the years some of the original paint came off. Those areas were sanded and new coat of paint applied over the entire bottom. in Deltaville. Now it is time to sand off the entire paint. My question is the boat has never had any blisters so should I sand the bottom good and apply new paint or should I let the yard apply a barrier coat before the bottom paint?

My boats PO had Interlux barrier coat installed last time a bottom job was done, they took it down to the Gelcoat, now I have "Pox" to deal with.
I feel certain that there was some moisture in the Gelcoat, and that the epoxy sealed it in and that is the cause of the pox.
Unless you can leave her out for a considerable time, I'd leave it alone, right now you have nothing to fix.
What does the factory recommend?

Of course mine is an old boat with I'm sure different resin, either way I believe even the new Gelcoat is porous isn't it?