Petsmart has Python water changers for about $30, and given the sheer amount of work they eliminate, they are most definitely worth the investment. Also, it's pretty much impossible to spill a hose, so no worries about accidentally dumping water on the floor.
Well- no worries if the tank filling is supervised. Do not do anything distracting while the tank is filling or Murphy's law says you will regret it. I'd suggest grabbing a book/computer/etc and sitting somewhere facing the tank. And yes, I'm speaking from experience.
And, as mentioned above, your South American fish might decide to spawn if you add cold water at a steady rate. At the very least, they'll look interested in each other. And it's pretty much the trigger for breeding many species of cories.