RE: Herculiner
I did it to my 97 Wrangler many years ago...went on great and was *very* tough. You might need to re-apply in the foot-well areas after a year or two (it does wear down), but this is a simple touch-up process.
Mask off the areas you don't want the liner getting in (including floor panel seams). If it's removable, take it out and mask (if needed) it outside the vehicle and coat it that way. Carefully tape off the back side of panels around the edges to make sure you get a clean edge. Once dry, use a packing knife to score the masked areas before peeling (it'll just rip the tape otherwise). Plan ahead....once that stuff get's on, it's tough getting it off.
I used a scotch-brite pad on a die grinder to scuff up the paint surfaces to get things to stick. Use a hand pad for corners...prep work is critical here, or it will flake off. Consider using some TSP (Trisodium phosphate) to get things squeaky clean (use caution...this stuff is dangerous, but works well).
Remember, this stuff goes on with a roller to get the texture right. It's thick going on, and very tough once it's set up.
Note, the fumes are pretty bad for the first few weeks (well, at least they were for me)...leave the windows open to allow the out-gassing to dissipate completely.
Hope that helps...