As for working on Fenders and other tighter areas you will work them much like you would a larger flat area. You want to keep the pad flat to the surface, however it also helps to have varies pad sizes to use in those tighter areas.
There will also be areas that you will just need to do by hand, such as the cups behind door handles.
These areas almost always have scratches, and in most cases are removed pretty easily just using a microfiber rag and compound or polish by hand.
I am going to be doing our Optima here in the next few weeks as it has been almost 2 years since I originally worked on it, and will put together an in depth write up of the process with lots of pictures.