I've thought about this, but haven't gotten as "high tech" as some of you. I'm using the "keep it simple, stupid" method ... (my wife always recommends that I use that sort of method!) No transfer pump, batteries to run down, etc. I just use gravity and patience.
I rely upon the blue Aquatainers ... but I just bought a hose barb that screws into the cap where the spigot usually goes. Attach a small food-grade vinyl hose, put the "jug" on tailgate or picnic table, etc., run the hos a little way down the water inlelt's fill tube, and go have a beer. Few minutes later, the water's in the tank and all is good once again.