I went to spray the interior metal passageways of my 240Z hatch with a Transtar Amber anti corrosion spray can and noticed there is a reinforcement plate on both sides and top of the hatch. To spray the two passageways on the sides was easy as I just had to guide with my hand the 3 foot long spray wand above and then below the reinforcement plate as you can feel the end of the plate with your hand. See drawings. After I did this on both sides I drilled a couple of holes at the top middle of the hatch to give access to the top and bottom of the reinforcement plate in that area. Access to that area can also be had without removing the hatch as I did by drilling in the corner, see last drawing. Be sure the two corner holes line up with the two passageways at the top of the hatch especially if you use the Transtar spray wand as it isn't flexible enough to go around tight turns. I plugged the holes later with plugs I got at an auto parts store and sealed them with silicone. The animated .GIF drawing shows the location of the reinforcement plate. The end of it can be seen by looking up in the bottom inside area of the hatch with the interior finisher removed.
Black U shaped area is reinforcement plate:
Where I ran the spray wand on sides of hatch:
Drill two holes for spraying top of hatch:
Amber Spray can:
Wand used was: (find with google)
#4460W Amber Rustproofing Wand