I'm glad you got your friends trained. For others just getting started the easiest way to train older hens to use nipples waterers is this: Set up your nipple waterer to work as directed, then unscrew the nipple(s) to where it leaks enough to drip consistently every few seconds. Remove all...
I just unscrew the individual nipple so they leak a wee bit, just enough to drip once every few seconds. Do this for a day or two with their other waterer taken away and they figure it out real quick. Then just screw the nipples in all the way once they've got it.