On large SUV's (i.e. Escalade's, Excursion's) I open a door and just pull my self up on to the roof. Once I'm safe and up right I have a helper pass up a full 5 gallon bucket with wash solution and a push broom. Mind you, I'm a big guy (think 275lbs 6'3") and I wouldn't be able to get the entire roof without walking around on it. Hope that helps!
:laugh A good long step is a real saver.
