I own a shop and spray on regular basis,I like using slow reducer and very slow hardener when shooting any type of paint,metallic or solid color,base/clear or single stage.It allows a much better flow out and nice smooth finish,most paint nowadays have flop control additive ,it controls ther metallics helping to get them to be more stable without mottling and blotching.It's been a long time since I had metallic control issues,

when spraying metallics,first coat 50% overlap,25% on following coat(s) ,every coat must be sprayed in X in relation to previous coat,that means if you shot the hood in front to back strokes,next coat must be done in left to right,