looked at the instruction of primers. Some say 1 hour, some say 4 hours if temperature is above 51 and oil primer says 24 hours. Whey you paint, when you are going to recoat the primer? I am sure nobody looking at the clock to do that. but how do you know it's time to recoat now? just touch the sureface, if not stick it is time to recoat? I am talking about exterior wood paint.