I'm planning on using the roll on herculiner on my truck bed but the floor has some pretty heavy surface rust and areas where there is NO paint left. I'm unsure of the best way, beyond sanding, to prep it for the liner. Should I use some sort of rust treatment? Should I prime it? Do I need to paint it before I put on the herculiner? Sorry for my ignorance but all the instructions for applying this type of liner seem to assume that you have a nice new painted bed to start with....
Also, I really want this stuff to stick so any recommendations on a final sanding grit would be greatly appreciated! (This scuff it with a scotchbrite pad sounds WAY too simple.)
Thanks!