You say that a 36grit disc wont touch it, have you tried a 7" sander and the 36grit on it, if not try this on one of the corner, but be careful as you can easily distort the panel.
(Are you sure it isn't a fibreglass bonnet
Oh that was uncalled for
Sometimes the DA sander is not enough to remove the black factory primers. Different manufacturers use better quality paint than others, some get it at a lower price for good quality etc etc etc...............
Let us know if you succeed with this predicament
When a car has a long long session in a panel shop (like 4 years) it can quickly become contaminated with different products and chemicals that float around in the air from other types of paint, fillers, silicon's (although not the painters best friend) and even certain hand cleaners, not to mention your own hands. These can fix themselves to the car body and some degreasers don't remove 100% of this causing long term effect on the finished paint work.
Never say, 'There's no rush' when you take your car into the paint or panel shop. Then again never say, 'I want it back yesterday'
