This refers to how quickly the auto paint activates and begins to dry. For example, a slow activator will take longer to dry, which will be helpful if you’re painting in hot weather, as it will ensure you have time to spray all the paint in your gun before it dries up. Conversely, if you’re painting your car on a cool day, you’ll want to use a paint with a fast activator, to ensure your drying times are not too long between layers. If you’ll be spraying in moderate temperatures of 70 - 80°F, choose a medium paint.