this might help a little...
The gray area around the perimeter is sanded all the way down to the factory primer
The white smaller areas are sanded all the way down to the substrate
The black areas are the orig finish, just scuffed (mistake)
Unfortunately, I just stuck the scoop on with double stick tape before I blended the hood scoop in with body filler (another mistake)
I hope to have time to take a "do-over" this summer.