That's a nice looking Chevy sedan, and a great color choice! The trunk latch is protected from the weather, so like you say a few dabs of grease at the friction points would be a good idea, IMO.
If you do choose to powder coat for appearance I would think you need to disassemble the latch assembly first, which looks like it would be a chore with those rivets. I'd be more inclined to give it a light coat of primer, then a couple of thin coats of color followed by the selective greasing. For the inside of the trunk rattle cans might be the ticket if it's just a basic color.