I sanded till it was level, and like i said into the primer layer. If there's still a depression, and you have it clean, and can get paint into the bottom of the eye, it should self level. You may need multiple coats to get it completely flat. Maybe sanding between coats. Mine was on a basically flat surface and I shot about 3 coats before each coat was completely dry. It's the best looking spot on the cab.
