Hi Ryan,
I fill my loco through the blowdown valve, I'm guessing that you have a water supply other than a bottle! Makes it easy as you don't need to take any thing off & sure beats using the hand pump!
the only suggestion I would make is that you have tap at the engine end, before the flexible tubing you use to connect up with, why ? The first time you close the blowdown valve when the engine is fill & you don't you will find out!
Cheers
Kerrin