I have used "Simple Green" for cleaning up pipe and fittings/hardware on Medical Oxygen systems.
Never used it for A/S, but it might be worth a try. Perhaps inject in the pressure washer for a deep cleaning.
Does the A/S show up under UV light? If so, that could put you one step ahead B4 a paint application.
The fisheye is probably caused by silicone in the anti spatter.
We used to use "silicheck" when repainting cars [30+ years ago], it is a silicone paint aditive. It makes the paint wet the silicone and not make a fiseye, but it makes the paint run easily too.
You might check with an auto body supply and see if they have a cleaner for removing silicone.