For detail painting, I’ve always used Citadel (Games Workshop) acrylic metallics. They don’t have the ‘flake’ effect you mention and are generally regarded as pretty good. They brush on perfectly and are ideal for small bits on underframes, door handles and the like. For a metallic sheen personally I think you can’t beat ground pencil lead applied with a finger over a dark base coat - perfect for buffer heads etc!
Ive some airbrushable aluminium from Vallejo to try on a mustang for that NMF effect you mention - I believe a lot of these type finished including Alclad depend on a high gloss black undercoat to be effective, but I’ve not got any first hand experience, yet.