rocker cover n inlet n stuff ive always done with standard aerosol cans from halfords kinda deal, standard primer, the lot. its temp rating is easily capable of working on these sort of parts

exhaust manifolds and turbos i always use the VHT (high temp) aerosol cans, colours limited to aluminium or met black, sometimes a weird red if ur that way inclined, no primer needed, and lasts a fair old while so long as ur not constantly knocking n messing with it