Hi David: There are two inexpensive items you could use. One is a plastic "lip"that snaps on the rim of the can, after the lid is removed. It's ideal for pouring into trays etc. The one that would probably work best for you is a plastic lid that snaps on the gallon tin, after the lid is removed. It has a built in pouring spout with a screw on lid. ideal for the small jar you're eventually going to need to get it into. If Rona doesn't have them, try Cloverdale Paints. Just phone them and see if they sell them. I've used them for years.
Good luck.....Robert