We use both S4S and Park4night to find a suitable site and then just key in the relevant code to get the navigation route on the Garmin 780 Camper. Having keyed in the code, we just press 'Go' to start the route navigation. I do tend to save the aire/site as a favourite when we arrive, with the S4S Reference, so that any slight navigation errors are eliminated on next use [often use the same aire on the outward and inward legs of the trip.
Steve