By all means use a pressure washer to get the crud off, but don't use any form of brush on your paint.
I rinse the car with the hose (we have great water pressure)
Wash using Meguiars Gold Class shampoo (two bucket method)
Rinse with low pressure sprinklet nozzle
Dry with Auto Glym synthetic leather thing
People have different opinions on how to dry, but in my opinion this is what really finishes off the wash. If you don't dry it properly, it won't look good.
Also make sure that your sponges and leather are all clean. If the car is really dirty, or has lots of bugs, etc. it might be worthwhile to wash those areas first, i.e bonnet, below the waist line, wheels, then rinse and start again, having thoroughly washed out the sponge (or better still getting a new one).
You also need to be careful of watermarks from the water drying before you have leathered it off, this is especially a problem in hard water areas. I used to have a black Puma, and washing it in summar was a real pain, I had to keep the sprinkler on while I washed it, otherwise the bodywork would absorb the heat and evaoprate the water, leaving nasty marks. That was when I lived in a hard water area though, much better where I am now.