All cars are different and I'm lucky that this one doesn't get that dirty even when it rains. The Dodge Ram I had got dirty very easy. I use a damp cloth, wipe it down by hand then use 303 or Sun Of a Gun to make the plastic and hoses look good. Also keeps them from drying out. When it gets really dirty, I hit it with a hose lightly only on certain areas.
I keep mine like that too - and on this Scion, it's strangely easy compared to all the other cars I've owned.
I clean it about 3x per year, and it's always sparkling.
BTW, I have a polished stainless exhaust that I also keep shiny. I clean it about every 3-4 car washes, and it shines like crazy.
You're not German are you?