Keep It Moist
Exposure to the open air can cause acrylics to dry out even faster than usual – both on your palette and on your canvas. Because acrylics dry quickly, you must have a strategy to keep your paint wet and workable during a painting session. You will also need to about how to store your palette between sessions. Paint drying before you can use it is just money down the drain.
There are several things you can do to preserve your wet paint. Avoid purchasing those “stay wet” palettes. Get a regular white enamel palette. Put a couple layers of wet paper towels in the bottom of it, add your paint, then cover with waxed paper.
When you are done for the day, lift the waxed paper up a little bit and spray some water on the paper towels. For added protection, store the palette in a baggie with a slide closer and your paints will stay moist and ready to use. Keep a small spray bottle filled with water handy so you can lightly mist your palette with water as often as necessary to keep the paints moist.
If money is not an issue, you can purchase a Stay-Wet Palette. The palette comes with a sponge layer that you dampen and place underneath an acrylic film. You actually mix your paints on the acrylic film. The film stays wet because of the damp sponge underneath.
I suggest that you make your own version of the Stay-Wet Palette, as mentioned above. First, make a pile of 5-10 paper towels. Then use your spray bottle atomizer to dampen the pile thoroughly … the paints will be kept moist from below. Spray the paints as needed to keep them moist from the top.
The absorbent paper towels won’t allow for easy mixing, so you will need a separate palette for this. You can use a paintbrush or palette knife to transfer the paint to be mixed from your moist paper towels to the the mixing-palette.
I hope these tips help. Good luck and Happy Painting!