Vht paint and use the primer.
I soda blast the complete block including exhaust manifolds so i have a clean surface. Cover what I want left aluminum then psint the eest in primer. Let that air dry then paint the block one color and headers another. I often will paint the block one bright flat color and remove the aluminum acessories before painting the remaining acessories, brackets, pulleys, and manifolds flat black.
Vht flat makes for easy touchup if you smack a wrench against something kind of deal.