I located some pictures that came from this forum about 65-66 doors' paint.
A couple of points: these pictures are what I thought were important; masking and painting are not an absolute science, workers were under a time constraint to get the job done quickly, therefore no two cars were masked the same, just "similar".
I would assume the the masking was done from a "pit" alongside the assembly line and the workers were "looking up".
Jim