Will that stuff work on the bottom side? They only show it in use on the top side of the floor pans. I'll probably do the top side later, but for now, I just want to coat the bottom with something that will seal everything up, and be very durable.
check your favorite local paint store... they should have some sort of spray in bedliner product in a kit form, spray gun/coating/catalyst for around a $100-150.
We get this from our local paint store I beleive it's $6 per can. It covers very well and a can goes a long way. I would say you could do the whole inside, underneath with 6 cans.