What kind of car is most suitable?
Any car will do, as the trails are accessible. However, it is certain that the more basic the mechanics, the easier it will be to repair if problems should occur. Similarly, the lighter the car (e.g. Citroën 2CV, Mehari, 4L…), the easier it will be to push if you get stuck in the sand. One last point: the higher the ground clearance, the easier it will be to pass over rocks on the trails. But don’t forget that a car manufacturer is more likely to lend you a more recent model, since publicity for a model that is currently in production is more interesting than for one that is obsolete.