I know many people have different ways to organize painting days. I just pour the paints into little cups with lids. I get them fairly cheaply from a local restaurant supply store. The kids share the colors with the kids at their tables. They mix colors directly onto newspapers. When the class is finished, they learn to put the lids back on and return them to the counter. These paints last at least a month in the containers. When the paint is gone or dried out, I just squeeze out more paint on top. There is very little waste. After a couple months, I will end up having to throw away the containers, but not too often. If the lids are fairly clean, I will reuse the lids too. I put all the paint cups in a nice box and store them away until the next day we paint.