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Though I have grown staghorn ferns by the hundreds, I will have to guess the answer to your question since I have never (completely) removed the white, powdery, waxy coating on their fronds. Occasionally, some of this coating gets rubbed off but it has never caused a problem that I am aware of. My guess is that you'll want to mist the plant (perhaps) daily so that moisture can replace some of which will transpire from the fronds. Keep your plant in bright light but no direct sun. That will limit water-loss. Keep your growing media moist but be sure it is well-draining. Tropical plants in general love moisture but hate soggy soil. My hope is that the waxy coating will slowly but surely reform. It may take weeks and it may take months. I don't know.
Good luck with your staghorn. By the way, when the fronds get 6-8" in length, every single one of my staghorns are mounted. That's the way they grow in nature. They are air-plants.