In general, if you splash a few drops of water on it and it beads up, its too wet and needs to dry longer. If it absorbs, you can paint it that day or pretty soon. Also, if it is wet, set it in full sun and it will probably dry out in 1-2 weeks. If indoors (shop / garage), put a fan on it and it will probably take 3-4 weeks, no fan - 6 weeks.