Not having rented a 4x4 - but really wanting "to touch the desert" - I took on several occasions the pedestrian option!
Each time, following precautions:
- always park my car at the edge of a tarred road (to avoid soft sand!)
- go up to the top of the nearest dune to locate the neighborhoods and define an approximate circle of a few miles.
- leave for an excursion of several hours, taking along 3 or 4 liters of water, cereal bars and a compass!