Most hard paints are ineffective after a haul out. No matter how much you want them to work they are toast. If the paint becomes ineffective due to time in water or a haul out what is the point of having a hard paint under an ablative. It will be as effective as the barrier coat after the first season. It is a total waste of time if you are thinking it will offer any protection if your ablative layers wash away.
In a recent post on a similar topic I said I would consider using a hard paint for the first coat...may I retract that statement? When I did my bottom repair I used only ablatives, and now I am glad I did because what MS states makes total sense.
Below shows two coats of black ablative over the barrier coat, followed by one coat of blue ablative:
For the record, I spent the better part of a day sanding my hull using many 60 grit sanding disks after the blasting job was done. Maybe he didn't do as good as job as he should have blasting the hull? Maybe it was because there was years of hard paint build up, the boat is a 1982?
Dunno know, but the blasting did take off most of it (99%) and there was a lot to remove. I wanted to be sure, so I sanded till all I saw was pure white gel coat. So, three years now with the boat being stored in the water year round and I have found zero signs of blistering, voids, etc.
Here is what it looked like after he was done (yes, those a hundreds of tiny blisters about the size of a baby pea):