Why am I having pin holes in my three-part acrylic enamel mixed exactly as instructed 8-4-1?

the pinholes(fisheyes) may be causes by a contaminant on the surface of the primer coat. silicone i usually the main cause but it may as simple as not cleaning the surface with a quality wax and grease removing solvent.

check with your paint supplier as to which one is recommended for the brand of paint you are using.

before resanding, wash the panels down with the solvent.

ensure that you remove anything that may have come into contact with any form of ARMORAL (PURE SILICONE) from your work and spray area.

sand down panels and wash with solvent prior to wiping with a tack rag.

hope this helps