SierraGlow "SG"
http://www.sierraglow.com/ or PPS www.shinenshield.com
Washing the car yourself is a must if you wanna take care of your car properly - no short cuts. Outside car wash do not and will not dedicate much effort to ensure its "correctly" washed. Why do I say this, is because they use the same old/worn cloths from 1 car to another, so imagine how many dirt, sand and dust particles they carry from one car and to another and another and then to yours? This in the long run will scratch the paint, and you see plenty of swirl marks/"spider webs" under proper lighting. It will surely spoil the shine after SG.
So by applying proper washing technique, regular maintenance and use correct tools will ensure your car is well taken care off, and you know it is because its washed by yourself.
So if you are really into doing the wash by yourself after SG, I would recommend that you try
1. Optimum No Rinse Wash & Shine (ONR) - Just rinse your car properly, wash 1 section of the car each time (top 1st then to bottom) with this ONR and then wipe dry, no need to do any rinsing. Its surprisingly cleaner than normal shampooing products, slightly pricier than conventional car shampoo but its well worth it for me. If you want to buy this please PM the seller KC
http://forum.lowyat.net/user/344336 for more info.
2. Use 3 Microfiber towels, 1 to wash and 2 to dry, whole car can be washed & dried within 20mins. Towels should be replaced after 3 months of usage.
3. Wash with 2 bucket system, 1 with ONR/shampoo and the other bucket normal water to rinse the towel after washing each section to remove any potential dirt/sand/dust from the towel before proceeding to the next section of your car.
For me using ONR saves time and effort, so with SG and ONR is doubly easy to wash and maintain your car regularly.
As for the tar question, it is a tricky situation to handle, it does stick to the surface on the car even with SG, what you can do is to clay the tar spots and it will come out, if the tar is like a big patch/splash then use the Tar Remover or Optimum Power Clean straight or if you have the time go back to SG, let them handle it for you if you worry about damaging the SG layer, which means probably you have to leave the tar stains there for some time before they have slot to help you, so either DIY or go back to SG. That's why its tricky...

Thanks to Sothy for his detailed information sharing. Really appreciate that. Many thanks!