They sell 1/2 pint with a brush on the lid. If you're just doing one car, this should be plenty. Other than door weather-strip and trunk lid seal, this type of glue was used in other areas such as:
-Headliner
-Carpet on bottom of quarters for fastbacks
-Attaching insulation to back of kick panels
-Gluing down the luggage protector in the trunk
-Roof rail weather-strip
I might be missing more, but keeping it to '66 models
BTW, the 3M glue is useless for this type of thing. Another trick is to wipe off the contact surface of the repro weather-strip with some solvent. Also, roughing it up on the contact edges with some 180 sandpaper will help give more bite to the glue. When applying the neoprene adhesive, do about a 12" section at a time