'I am about to attack the car with a sponge '
Nooooooooooooooooooooooooooooooooooooo.
As C WRX says try to get a wash mitt, preferrably a lambswool one( dear, but worth it) or a microfibre one, and use the two bucket method if you dont have a grit guard.
2 bucket method: 1 bucket with shampoo soloution, 1 with clean water. wash a panel then rinse mitt in clean water,giving it a rub to remove debris, then on to next panel etc etc.
Hope this helps too mate .
cheers
Iain