I bought Eternaprime in a spray can and a hard rubber roller. I applied it over 15 year's of Dicor on my old trailer, did just fine. My suggestion is to clean the roof well to ensure proper adhesion. Don't stretch the material (it loses its ability to adhere when stretched). Apply on a warmer day and use a hard rubber roller. Roll it thoroughly and with force to fully set the adhesive. It'll last longer than your trailer!
If you want to be extra secure, pay to have a pressure test done AFTER you Eternabond it. That way you can be certain you have everything sealed correctly. Good luck!