One of the things that is confusing to me is in the pics I posted on this thread. Looking at the pics of where the inner fender and fire wall meet is the appearance of red oxide primer under the black. So, red oxide the entire engine bay and underside of the car. Then if you come back with the batch primer and coat the underside of the car and the engine bay gets black paint, the red oxide should disappear?
No the red oxide would have not bee applied to the underside of the car behind the firewall to floor seam but in front of it in this example
I don't see a posted picture of the inner fender area just the bottom of the firewall (transition) to the floor The firewall along with the engine compartment and the inner fenders on the wheel side and the jets from below would have applied the floor color - in your case the batch color - black
Depending on the height of the painter and the effort he wanted to put in that day (moment) they didn't always bend over allot or reach the area between the vertical section of the firewall and 100% of the transition area between the firewall and the floor sections. This often created light to heavy overspray. During cleaning its not uncommon for someone to remove/clean away 50% or more of the engine compartment black from this area from my experience.
Scrubbed too hard many a time and rinsed off the paint
