how much POR15 do you think it would take to cover most of my 86 blazer frame? For now I'd only be applying it to the areas at which I can get at. I have the floor completely removed.. (well almost) so Painting the rear most portion of the frame, up to about the firewall, or perhaps the seats will be no problem. How long is the shelf-life of an open can of por15? It's expensive too, so I only want the amount I'll need. I appreciate any input! Also.. is this stuff hard to use and apply?? Thanks!!