Scott, I disagree. Enamels do not necessarily cover better, especially in white and other light colors. Hide, as it is properly called, is related to pigment load and pigment size. When a paint is reduced for spraying, pigment load is functionally reduced.
To get better hide with white, paint silver first, then overcoat with white. Metallic paints generally have tremendous hide, and lend brilliance to a white overcoat. For yellow, use gold metallic.