No, you don't need to prime the floor. Get an orbital sander and go over the entire floor with about an 80 grit sandpaper. This roughens it up and gives the herculiner some "tooth" to adhere to. It took me about a half hour to sand an 8 x 18 foot floor and a ramp door.

Rhino lining is WAY too expensive. It would have cost $800 - $1,000 to have my floor done. The herculiner is very easy to apply. The trick is to stop and stir it about every 10 minutes to keep the particles floating.

The other thing is the smell. This stuff smells like it would kill you. It is the strongest and worst smelling chemical I've ever used. Do the trailer outside with a slight wind and wear a paint respirator. Even with the respirator it gave me a nasty headache.

 

This is a great idea with the bed liner stuff. When I eventually get an enclosed trailer I'm going to do this right away.

 

the bed liner idea is cool but if you arn't rich then i would sugjest just a heavy duty paint. A good paint (and what i used) is marine paint, water proof and very thick to last a long time.