Just food for thought. Dark metallic, dark primer, light metallic, light primer.
When I had my sign shop in the States, too many years ago, I used to spray panels, and some vehicle graphics along with back painting lighted sign faces. In spraying my metallics the first coat was thinned to spray and cover. If sprayed with too much pressure, and to close to the panel, the metalic would bury itself, in itself below the surface. This left a rather uneven metallic finish, distinctive lines of metallic. With this first cover coat still tacky, but not wet, the final coat was thinned just a bit more, sprayed from a bit further off in nice even strokes to cover. This lets the metallic flake float onto the surface evenly and the additional thinner lets it melt into the covering coat. If I was spraying a big flat panel the strokes would be horizontal the full distance of the panel, slightly overlapping, then vertical overlapping slightly.
Like I said, just food for thought when approaching metallics.
*Always spray the edges and recesses first, this prevents loading of paint in these areas which create the runs.
Bill