Agree with above about protectakote.
I've just repainted my floor with a liter of it as it was scratched and peeling, have had the van nearly 8 years though !
Tbh though if you pick warmer weather you don't need to add a hardener, did mine the easter bank holiday weekend and was ready to go after the bank holiday monday. I've put a perforated thick rubber mat down now over it so I don't scratch and chip it so easily this time.
I wouldn't use it again though.
When / if I need a new van, provided the floor is in good nick I'd leave be and concentrate on making the system leak free.
after all its only exposed metal that if constantly exposed to water that will rust.
If ply lined floor and panels and I really wanted to waterproof and look pro, I'd seal it with a fiberglass roof kit - 5m squared kit with everything you need will do a mid sized van , readily available all over the net and fleabay for approx £70 ( comparable in price to protectakote but way more hard wearing and better looking finish )