Trying out some new paint - atelier interactive acrylics. They have an "unlocking formula" medium that you can use to prolong the drying time or reactivate the paint when it's completely dry. Although I've been finding that just water will reactivate the paint and let you rework it (though this may be with just thin washes? I'm not completely sure if it's a good thing..... I splashed a little wet paint on a study that had been dry a few days, and when I went to wipe it off, it took off the paint beneath it. And not in a way I intended! So I'm guessing these have to be coated when finished. It does open up a lot of possibilities!