I was going to publish something more private but I changed my mind.. So this will do for today's photo challenge: crap!
Instead of using a palette made out of wood, I use these paper palettes. I bought them in Spain but I'm sure there are something similar in the art stores here. When you're done with one of them you can just throw it away and next time you're about to paint you basically start on a new one. This way you do not need to clean! The only downside I've found is that it is white, many artists prefer another color of the palette.