Compounds are third level solution. I would recommend claying the marks first, and then using a mild polish or paint cleaner before moving on to a compound. If you could post a pic, I can offer better advice to whether you really need to compound the marks.
EDIT: As for specific products, any commercial clay kit such as Meguiars or Mothers found in Walmart, Pep Boys, Autozone will do the trick. Mild polish would be something like Meguiars SwirlX applied with a foam pad applicator (the yellow ones). For compound, I would recommend Meguiars Ultimate Compound, also applied with a yellow foam applicator.