Sanding floor pans Sucks

I've been cleaning up my floor pans this week. They all looked good except the drivers side front that I need to replace due to a few rust holes. I scraped the rubberized paint most of the way down and then sanded with 60 grit to get to bare metal. Looking for suggestions as to what to coat it with. I do not have a spray gun and was going to use the por 15. Whatcha think ? Or do I not need it since I will not be painting over any rust as it has been sanded off ? Other options ?
Thanks