I would think 3M would have a product in a cartridge gun type application (like a caulking gun cartidge for doing things around the house). A product applied out of a nozzle might make it easier to reach the area you want it to be at. If the nozzle is too short you may be able to extend it with something like a hard plastic tube or copper tubing.
I have not had problems with a hood skin coming loose before but on my roof skin on my 73 and 74 (and also on customer's cars with audio systems) I have cleaned the area and applied liquid nail to join the metal together or to allow me to glue in pillow blocks so trim panels can be attached to the car without making holes in the metal. The liquid nail does dry up rock hard and I have not had any issues on my roof beams with things like ghost lines in the reflection of the paint. On my 73 the roof beams were glued to the underside of the roof skin at least 10 years ago and they are still locked together solidly today.
The biggest thing under the hood would be to get both surfaces really clean to where whatever you choose does stick. A lot of oil and dirt can accumulate onto the underside of a hood.
I used urathane put it in and brush it out with an acid brush.Not correct for a show car but looks fine and got rid of that noise when closing the hood.Its black to boot.Careful using stuff that swells or it could cause some high spots in a soft point of your hood.Skull