Westy I've found that by using foam(see below) with my pressure washer its cut down on the amount of time spent with a mit(see below) the cars then cleaner when a cloth/mit is used which equals less swirls.
In effect your pre-washing your car I've found that often the prewash is sufficient to have the car looking clean, so often I don't need to bother with a bucket and cloth(see the drying cloth they are well worth it too imo)
Its not cheap initially but the following products do work and well, HTH

http://www.cleanyourcar.co.uk/washin.../prod_371.html

http://www.cleanyourcar.co.uk/washin.../prod_370.html

http://www.cleanyourcar.co.uk/washin.../prod_282.html

http://www.cleanyourcar.co.uk/microf...2/prod_84.html

ON the swirling on a black car, I had the same on the paintwork on the RS Turbo(which is black) I used Sonus Clay(green) & clay lube and it made a huge difference.
Clay
http://www.cleanyourcar.co.uk/detail...2/prod_37.html

Lube
http://www.cleanyourcar.co.uk/detail...t/prod_42.html

Its then a case of waxing and polishing to bring back the shine.