As said before. Crap detergents, grit on the brushes and poor rinsing can only result in scratches and swirls.
Garage pressure washes are a waste of time. You can do a good job with just the lance cos all that does is moves the dirt around, and the brushes will have undoubtedly been dropped on the floor by people before you.
Hand car washes can be just have bad. Most of them still use sponges, and if they do use mits they are never washed out, and lets face it, it they're washing 4-5 cars an hour, they're not going to be that fussy.
Best bet it to leave it until you are able to do it yourself properly. A dirty car will always look better than one that has been cleaned badly.
