There will come a point when it is obvious that this is as far as the person escorting you will go. This may be outside the front door, half way to the reception area or even to the car park. This is the point at which you must bid them goodbye. An appropriate way of ending the encounter with them would be to say, "Thank you for seeing me out. Thank you also for your time and I look for to hearing from you again." Smile and shake hands as you say this. Be sure to make good eye contact with them.
Turn around, walk off and don't look back. Proceed to your next destination, hopefully with a sense of satisfaction stemming from an interview that went well.