Thanks for the vote of confidence Chic. Hope I don't do anything to lose your trust! In my experience there is no need to shoot primer over the spot fillers. However, I am shooting nothing but solvent based paints such as acrylic enamels, dope, epoxy, the old Chevron Perfect Paint, etc. Other than one project with Warbird Colors I have not tried any of the water based finishes so can't comment on those. If in doubt though there is really no reason not to shoot on a light coat of primer before base coating.