A length of rubber hose works well for contoured areas. I prefer the softer 3M pads over the hard arched blocks. Your local auto paint store should have a good selection.

I can't imagine being able to sand waves into a car with 1500 or 2000, or for that matter even 600, unless the person is either using their fingers, or the bodywork wasn't right and is revealed by blocking. Wetsanding should not be aggressive.