No special buckerts or spouts needed guys...
Just a new gallon and the one your about to finish up.
Add your diazo and stir, then simply pour off half the gallon into the old bucket and put the lid on. It's really easy to pout out from a 1/2 gallon and just as easy to hold the scoop coater over it pour out what's left in the coater.
When you empty that 1/2 gallon, open the other 1/2 and repeat when you open a new gallon.