In MD, you need to have the unloaded gun in the trunk, and the ammunition in a separate container. Start the trip this way, and arm yourself when you get to VA.
Driving through SC, you can transport the gun the same as in MD, but it's not necessary: it can be transported loaded in any closed & latched container (center console, glovebox, or a locked metal box).
Reviewing the PDF files at handgunlaw.us is always recommended.
I am not a lawyer. Your mileage may vary. Actual mileage will probably be less. Offer not valid in Alaska and Hawaii.