Outer heater box refinishing

[1970Tex]

Anybody have any luck refinishing the fiberglass outer heater box? I media blasted it with 60 grit aluminum oxide at a distance to prevent fiber breakout, and clear coated it with Duplicolor matte clear (with UV protection), and the whole thing fish-eyed. I sanded that down with 220, then maroon scotch-brite (about 320-400), compressed air, tack clothed it, and got the same result. Its almost like the clear is not compatible with fiberglass.