I have a giant chest freezer. I made room in one end for a plastic tote. I since the bottles with hot water and a quick wash with dish soap then into that tub.
The food is separated by a cardboard barrier that goes top to bottom.
Yes it takes some work and is not without contamination worry.
No. Like the electrolyte powder available in the poultry department at the feed store. SAV-A-CHICK also works.
https://www.mypetchicken.com/catalog/Baby-Chick-Supplies/Sav-a-Chick-Electrolytes-and-Vitamins-pack-of-3-p1136.aspx
I would think pie pans, the old style roasting pans (I find them at second hand stores) or anything 2" deep or so will work well. In training them to use them you may need to set the bird in and gently control the chicken. It takes a very short time before they realize it feels kinda nice.
Hydration is key with my flock. Giving electrolytes in the water helps. When they are drinking more and eating less they can get out of balance.
I also give mine watermelon.... Not to much mind you. They will tend to load up on it and have reduced protein intake because of that. I give half of...