Great suggestions for marking the trail. One spot that seems to give people difficulty, even during daylight, is on trail 3W02 after leaving the forest. The trail marker there needs more support...keeps coming loose...but is pretty clear. From there the trail is easy to follow until you reach the last big hill, where you must turn left and climb. Another trail keeps going straight there, and could be where this group went wrong. Sometimes people put a line of rocks across the wrong trail to hopefully guide people the right way. If a beacon light were to be used, I would think this would be a good spot.
I feel sure that the DCV group would be happy to help with marking trails as long as this activity is USFS and/or BLM approved. FOJF would also be likely to help with BLM trail marking.