I use a power washer, followed by a hand wash using the 2 bucket method. Autogylm shampoo. Followed by claying use menza clay and dodo juice lube. That will remove 90% of the tar. At this stage you could use the tardis or the holts detarrer stuff. Hose down again at this stage.

The paint should be sliky smooth now just ready for the polishing. I recommend the Autogylm SRP polish as it's a hand polish but can be used on a D/A too. A sealent such as Autogylm EGP would protect the polish. If you get to this stage your doing very well. A waxing would usually be the last thing to do. Loads to choose from on cleanyourcar.co.uk .