yah... self wash is best as no need to queue...
just did my wash / wax today... spent close to three hours... 
yeah .. is the best but could be time consuming and not all could afford the time.
3 hrs a bit long leh .. i did all you have done plus interior in around 2 hours.
By the way guys, another reputable car wash is the caltex opposite nee soon camp along sembwang road. See a long queue on the first day of CNY.