I've used the FloJet G70 to fill my Mori. I have hooked it to the bottom valve, but found it a hassle, so I ended up putting the hose through the top. That way, you keep an eye on it and close the valve on the FloJet when full.
You may not have the set up for this, but elevating a tank for the gravity filler is the best. We've started putting a tote on a platform just above the filler, gets us constant flow. The Mori has a float valve that (mostly works) cuts off the flow when full.
Cheers,
James