It flows pretty quick honestly. A few minutes for all 5 gallons. Just know which way the tube naturally bends so you can push it up against the side of the can to get it as far down as possible. I've thought about carrying a metal tube to put it in so it goes all the way down but have yet to do...
I use Wavian/NATO style Jerry cans myself but they still have the stupidly frustrating nozzles to use. I get around it by using a safety siphon which actually means I never have to take the cans off their mount ever. Wonder if that'd work the same with these rotopax or if the screen is a...