Martin,
It seems as if the lowest fuel consumption would be obtained by timing the coast, with the transmission in neutral and the engine off, so that the car came to a stop at the desired spot with no engine or wheel brake application, so that very little of the energy that went in to accelerating the car went up in heat. Easier said than done. It seems that using the brakes, either with the engine off or idling in neutral, would use less fuel than using the engine as a brake with the throttles closed. The hard manifold vacuum with the engine rotating above idle speed will probably pull more fuel through the idle fuel ports than would flow at idle speed.
