There is no virtue in doing anything the hard way. I'd rather work smart than work hard. I pretreat my water and then pump it to my tanks. I have a remote control that I use to turn the pump on and off so I can be in the room to watch the tank filling. I have several hoses so I can drain a tank while I am filling another.
My record so far was to clean eleven tanks and refill them in under two hours. I know I did better but I don't regularly time myself.