I had only two problems following ACA's directions on my TransAm; once in Charlottesville, VA (I kept going west until I found the right road), and once we missed the "unmarked turn" and had to come back after about a quarter mile. (There were locals on the porch waving at us, and we just waved back the first time by.) The turn in Missouri where you were supposed to read the number off the rusted plate on the telephone pole? No problem!
I do recommend you pick up a state road map from the first visitor center after you enter a state; it gives you a bit more perspective and options for alternate routes.