has anyone had any sucess using any other brand besides merc. spray paint that seems to hold up to fresh or brackish water conditions? what primer would you recommend using ?

I used Martin Senour black acrylic enamel with Ultra Urethane Hardener. Came out like black glass, lasted all season and still looks the same. Used a green marine primer (rattle can).

I've had good luck using the self etching zinc chromate primer (the "green" primer) and the Merc black enamel. Getting the surface clean prior to the primer is important.

Hematite, where did you get the paint?