Body Work Tutorial

I'm working on the engine bay of our charger project i filled the holes for the blower motor and heat+ac lines and smoothed with filler the rest of the bay is going to be hand stripped to bare metal [lots of spray bomb paint ect.] should i use etch primer first or go with epoxy sealer? I'm not sure what to do and don't want to spend time and money uselessly and cause myself more work and time. I have done the door jambs and trunk jam down to bare metal and covered with cheap primer just to keep from rusting [don't want to do that to the bay too many nooks and crannys].