Finishing an Outdoor Shower

Submitted to Community Café

I recently built an outdoor shower out of pressure treated lumber. As you can see from the photo, the posts were pre-finished. I primed with white latex Killz, and painted with exterior white latex paint. I haven't done the siding yet. Should I continue with the same materials (I'm not 100% happy with how it came out!) Or is there a better way to finish pressure treated wood? Best, Tony P.S. I live on the NJ Shore