I think it was gacknar? of full size bronco did a comparison of rust bullet and por 15. I don't think he was impressed with the por 15 either.
My situation was maybe a little different. I did the windshield frame. followed the directions, used the metal prep and marine cleaner. Painted it. Installed the windshield.
couple weeks later the windshield was leaking.
When preparing to seal it up I gently pushed on it and it came right out. The paint did not stick to the POR 15. Paint was stuck to the urethane on the windshield. Por 15 stuck to the truck.
Called them. They said I need to scuff it. Originally since the time frame between application and paint was so short the instructions said no need for any other prep just paint.
Tried again, same result, going down the road the windshield was letting air in. You could hear it and feel it. Again, paint lifted right off the POR 15.
Called them back.
Ground it all out and started over from scratch.
Again, 2 weeks.
Went through this like 3 or 4 times. Windshields aren't cheap. Geez the urethane wasn't cheap, luckily I didn't break one. I hated ******** around with it.
Finally sanded all the POR15 away, primed and painted like normal and no more problems.
So it may be a good product in certain applications but not for every application.