Yes, plan a minimum of 2 gallons if you want it thick enough. It took me 1 whole gallon to do the cab floor (not including the bed area) of my K5. And I was scraping the bottom of the can for the last bit.
But, my floor doesn't look like Adam's BII. Sorry dude but Ryoken's right, it looks spotty. Pics of my Herc before/after can be seen in the seat thread in the tech articles section.