Nobody ever actually showed you how to do this
Most people think a proper wash needs a pressure washer, a foam lance and half a Saturday. It doesn't. It needs the right chemistry and about ten minutes.
You learned it from your dad, or from a bloke at a car wash, or you just worked it out. Bucket, sponge, washing up liquid if you were desperate. It got the dirt off and it looked alright when it was wet.
Then you saw the swirls in the sun and assumed you needed better kit.
You don't. You need a different order of operations. Here's why.
REASON 1
Pressure doesn't lift dirt. Chemistry does.
A jet wash blasts water at loose grit. It moves it about. What actually lifts bonded dirt off paint is dwell time - a pre-wash sitting on the panel breaking the bond so it can be rinsed away.
That's chemistry, not pressure. A garden hose rinses just as well once the chemistry has done its job.
This is why professional detailers spend more on product than they do on machines.
Jet wash
Foam + dwell time
REASON 2
£300, plus a hose reel, plus somewhere to store it
A decent pressure washer is £250 to £400. Then a foam lance, then the right connector for your tap, then somewhere in the garage it can live.
If you're on a terrace, in a flat, or parked on the street, none of that works anyway. No outside tap, no plug socket, nowhere to coil forty feet of hose.
Two sprayers and a garden hose fit in a cupboard.