After all of that

Even after grinding into the rear deck around the fuel filler to remove them, there are still cracks visible through the primer.

The only real solution is to gouge them out with a rotary tool, so that's next. Not a huge deal and it will take care of these once and for all. The front clip is so much worse so learning how to defeat these is going to pay off when work begins on that part of the car.

The rear clip looks really great after another round of block sanding. Aside from a bit of work to dig these cracks out so they don't show up later, this is ready for some final fine work and then paint.