Foam cannon on a pressure washer is great (and fun). you can find a decent one on amazon (I think I use an older version MTM) what makes ease of use is no lance on the pressure gun. So if you can do pressure gun->foam cannon, its way easier to use than gun->lance->foam cannon. You'll have to mess with fittings to get everything to attach but worth it IMO
But - that's a warm weather wash.
When its crappy/cold I use waterless wash 3 out of 4 washes.
if you go this route get a pump sprayer, you don't need fancy, I use this guy ($11 vs $30):
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
You'll need a stack of MF towels too, you go thru 1-3 per panel.