I only wait until the coat is tack free, which is generally just a few minutes. The coats bond well to one another, and as long as you give them enough drying time afterward, there is no issue that I've run into with this method. Prints can be handled within an hour or less, but make sure to give it longer before you roll it up with tissue, as that can sometimes stick (although a damp cloth will remove any residue that sticks). Things dry pretty quickly in Hawaii, but I try to wait overnight before stretching, unless I'm in a pinch and have to speed the drying up by placing it in the sun. I pushpin the prints to hollow core doors for spraying, so it is easy to move them around, as needed, for the spraying and drying process.