painting inside the trunk

I disagree with the POR15 statements.

I wire brushed the surface rust in my trunk, painted it with POR15, primed it with the POR primer and painted the trunk with the Sublime body color. That was over 5 years ago and 30k+ miles and other than dust and dirt the trunk looks as good as the day I did it. I also did the floors in the car with PO15 and when I had the carpet up last year to add another layer of sound deadner the POR was still in great shape and not lifting at all.

If your trunk has any surface rust at all it needs to be completely removed unless you use a product like POR15 or the paint will lift. If there is no rust then POR is not necessary just use a good quality primer/sealer under the top coat.