I think a pressure washer and a foam cannon are worth the money but as like most things, we all have our opinions, needs and wants... so this is just make take on it.:dblthumb2:
I use an electric Karcher K7 and a MTM foam cannon FWIW
I had purposefully allowed my daily driver to get dirty so I could do some product testing whilst on leave recently - at the point I snapped the below set of pics, I'd done about 3000km in the 5 weeks since it's last wash (wheels and paint hit with Gyeon Wetcoat).
Here is what it looked like before :bolt:
I then pressure rinsed the front fender and wheel and dried it with a blower afterward
I then applied some Valet Pro Advanced Neutral Snowfoam via the cannon
Allowed it to dwell for 4 mins
Then blow dried it again
This 'pre-washing' definitely removed a lot of dirt that would otherwise potentially contribute to swirls....so for me, it's definitely worth doing.... I know there are guys like 'Accumulator' on Autopia that make use of the cannon differently (with a boars hair brush) and also guys who are able to effectively wash their car WITHOUT a pressure washer and cannon.... so while it works for me, there may be other methods out there that work for YOU (and others).
Hope this helps a bit