If you have access to an air hose to blow off the topical dust, a strong leaf blower works.
Dampen a cloth and wipe what you can, rinsing then wringing out excess water. For oily bits I'd wet a cloth with Simple Green, wipe, rinse repeat then dry off with a dry cloth.
No rinsing off with a hose, ever. Can always use a soft brush or a stiff bristle on heavier crud. Blow off, use a damp cloth to get remaining grime.
Now, wipe every time you wash the car because you've done the hard stuff.