Using water from a hose will not work in this heat. It takes quite a while for all the hot water to run out of our garden hoses and get to the cooler water before I can refill the chickens' waterers.
I'm a little surprised that people are having trouble to get their chickens to use nipple waterers. You have to stick their beaks up to them to activate the water a number of times and watch for them to swallow. Once one or two birds really get the idea, they teach the rest. You have to provide the "normal" water source during the brief transition. We even teach our young chicks how to use them by the time they are about 3-4 weeks old.
We use this large plastic cooler that has an extension of several feet with a number of nipples attached. That extension is wrapped with insulation to help keep them running longer in the winter. We have both a circulator and a bird bath heater in the cooler (the heater is obviously off now). The water actually circulates down to the end of the extension and back thanks to the circulator and the way the extension is constructed. If DH still has the link, I will post it later. I understand it, but am not a whiz at explaining its construction. All I know is we are happy with it.
We supplement the cooler/nipple waterer system with a tin can heater when it gets really cold. Those are awesome. We even used a 3-way bulb in ours so we could switch control how much heat we needed to keep the water from freezing. The best waterers to use on top of the tin can heaters (really not tin cans--decorative tins about 10" across is more accurate) are the galvanized metal ones that come from 2 to about 8 gallons but are the same diameter. They just vary in height. We may have to get a taller one this year. Last year we got by with refilling the 2 gallon metal waterer daily to every other day. We do not recommend using plastic waterers with the tin can heaters--we melted the base of one a couple of years ago.