Does anyone know how to clean the exterior of the exhaust without scratching it?

I know it doesn't matter after installing it, but just a curiosity on how to get rid of tar stains or harden stains as shown below:

 

for exhaust piping, i normally use a metal polish.

 

what kind of metal polish? does it gets rid of stains like those? and do you get it from home depot?

 

go to pep boys, r&s strauss, autozone... watever. it should be around where they have the was and stuff. or just ask someone for metal polish. about 5 bux.