Do you find yourself changing the water between paint colors too frequently? I may have just the tip for you. For a few months now, I've been using a KFC Go Cup as a water pot. Why? Let me explain.
First of all, the food inside when you initially buy one is probably
going to be delicious. And second, they're less than $3 each - making the cups themselves relatively free.
They're about the size of a coffee mug, made of sturdy plastic, and perfectly split down the middle into two separate halves. It also comes with a snap-lid cover, just in case you have a cat that likes to either knock things over or drink dirty paint water. (My cat does both.)
Simply wash it out and fill up both sides with water, stopping at the top of the divider, and boom! You can now paint for twice as long before needing to change the water. You're welcome.