I mix up a 10 pound bag at a time for convenience, I use 5 quarts of water to get a 1:1 mix. That makes right at 2 gallons which I refrigerate in plastic milk jugs. Then I just pour out quart jars, which I use for feeding, as needed.
I always put the quart jar in a bowl and run some hot tap water on it for a few minutes to take the chill out before giving it to the bees. Sort of like warming a baby bottle. :-D