No, it's not difficult at all. I got the idea from a pet waterer I bought with a smaller blue bottle. The key is that the water will only come out just far enough to cover the bottom of the neck of the bottle. After that the "vaccuum" holds the remaining water inside. As the chickens drink the water down, the vaccuum seal is broken (once the water level sloshes below the bottom of the neck) and a little more water drains out (and a bit of corresponding air bubbles in) until the bottom section is filled back up over the neck of the bottle, resealing the vaccuum. Along the same lines, make sure that you don't cut the bottom of the holes too low. The water needs to be able to rise far enough to seal the neck of the bottle without flowing out of the holes. (Otherwise you lose the whole 5 gallons of water on the floor of the coop).
So all it is, is the bottle and the 5 gallon pail.
The trick for me was to find a pail and a bottle that fit together nicely. The neck of the bottle rests off the bottom of the bucket by about 1/2". I suppose if you couldn't find a pail and a bottle that did fit so nicely, you could try the pvc pipe as shown in the picture with red pail previously. It would do the job of holding the neck of the bottle up off the bottom of the bucket about the same distance. Here is a closeup picture.
I fill the bottle, put the bucket on upsidedown and then carry it out to the coop (fairly easy to carry without water sloshing out). I do a quick flip (if I'm quick enough I don't lose any water) onto a crate and then carefully lift it onto the tin heater once the water is up to level.
That's all there is to it. The cost of the water bottle (I happened to have a few just sitting around anyways) and the bucket (I also had a bunch of those sitting around. So for me it was essentially "free" made from recycled stuff I had sitting around. And what I love about it the most is not having to worry about changing water every day. I know they say "super-clean" water is essential, but unless there are wood chips floating around in it, I don't think it's too much of a problem (at least I haven't had any). And with this arrangement, I have not had any wood chips in the water even with all their dust bathing and fluttering around.