How much you wait after red?
Answering that question won't really help you. To many factors go into how long you want to wait. How big is the nail? How big is the dab? How hot did you heat it in the first place?
What you need to do is just experiment when you get a new piece. Heat it, and wait a bit, then dab. Did the dab burn? Wait longer. Did the nail just cool off and let the dab slowly vape? You waited to long. Want the sweet spot, where it's just hot enough to fully vape the dab.