I make watercolor cards. Several at a time. For example, today I made 20 of them.
I often have paint left on my pallet. Rather than let it dry on the palette or wipe it out with a cloth, today I used my left over paint to paint a picture on the backs of the envelopes. Every envelope has a flower, leaf, something to give it a personal touch.
While this isn’t the most exciting frugal idea I’ve come up with, it did use up the leftover paint I had on my palette, which gives me a clean surface when I want to paint again. And why waste it if there is an easy way to use it up?