That does not look like blistering. Blisters occur between gel coat and fiberglass so it would appear on the bottom of the boat rather than the painted lead keel. Also, its practically impossible to pressure wash off all old paint and residue. It ain't that easy, I'm sorry to say. That said you have a pretty basic maintenance chore ahead. The keel can simply be ground clean using 80 grit to remove the remaining paint and scum. For the gel coat bottom, more care is suggested because sanding with too coarse grit or high-powered tools can eat right through the thin gel. Hint... be careful. You can use chemical stripper, in moderation, or you can scrape, or an oscillating sander and medium grit. If you feel comfortable using coarser medium... give it a shot... again though... go slow til you feel confident you're not going do damage to the gel coat. I prefer a variable speed polish type tool using 240 grit, foam pad, at a medium slow speed. Problem is dust though, so there can be restrictions if you're in a boatyard, or near other boats.
Once the bottom(that's the hull below the waterline) is clean, you can start rebuilding it. Here you a couple of choices. For instance, if you are thinking about racing, you might consider "fairing" the bottom to make it perfectly smooth and even (no bumps or depressions). Can you tell us what evidence leads you to determine the barrier coat is failing. There are no apparent blisters on the hull, and that's the primary purpose of a barrier coat. Nevertheless, don't try to strip the epoxy barrier coat... if you need, you can apply right over the existing. You'd be obliged to apply a chemical primer though...easy enough. But, honestly, once you decide on your plan of action... barrier or just primer over gel, then the anti fouling paint. You need to revert to the barrier coat and paint manufacturer's instructions and follow them explicitly. The barrier coat especially... because it is temp and humidity sensitive... bottom anti fouling paint is super easy, just roll on and discard the rollers after each use. Okay, good luck... you'll enjoy the project.
