I'm a big fan of gloss black coat as base coat for metal finishes. It is supposed to help reflect the metal color. I've tried it both ways and do feel the metal looks best over black gloss.With respect to metallic paint, I rolled the dice on Alclad metallic lacquers a year ago (having never used them before). I applied them to an ancient F100 kit I rehabilitated from the 1970s. Alclad recommends laying down their gloss black primer first. I'm not sure that's necessary or if it is just their means of selling more paint, lol But I did as they recommended and was very pleased with the results! So much so, I have some aircraft kits in the stash I'm looking forward to doing in all-metal and Alclad will be the choice for me.