Just bought and install a new Fiberglass door, The sales person at the Home Depot told me to used regular car wax in order to keep the door looking new.
Should I follow his advise or should I just go ahead and finish it with Clear Varnish.
Your door must be pre-finished, factory finished. Using a car wax will work. The only problem is refinishing later. It will be difficult to remove all of the wax. A good idea is applying a coat, or two, of varnish for extra protection. This will help fill and seal up any pores. You can always wax over the varnish for regular maintenance.