You say you blasted it. I assume that means soda/bead blasting, whatever. That result you have is pretty standard for a lot of boat...you basically knocked out deteriorating gelcoat
and/or exposed bubbles in the original gelcoat
You need multiple coats of barrier coat for it to be effective, at least four, more is better. It's not the kind of thing you want to skimp on as now is the time to do it right (unless you don't expect to keep the boat that long).
If it were my boat, I would put down one coat of barrier, which will then allow you to see much more clearly what is going on. After it had kicked mostly I would then run around with west system with 410 filler, filling every flaw I could find with a flexible scraper, trying to get it as fair as possible during application to minimize later sanding
. I'd then apply the remaining barrier coat layers, hot coating them for a better bond, fair any high spots from patching the then the bottom paint.
That's the quick way of doing it. A better result would be put the first barrier coat on and let it fully harden, patch (probably multiple layers to avoid dimples), fair the patches, then sand the whole thing with 100 grit and wipe down, then hot coat the remaining coats of barrier.