Did the bodyshop give you any indication as to how long to leave the car before washing?
Normally i think they recommend a few days on modern paints for it to harden properly.
Really all you need to do is give the car a good wash and then apply some sort of protection in the form of a wax or sealant.
The white dust you mention... is this in the panel gaps or on the car? i wouldnt have expected any from a decent body
shop, its polish dust from mopping the car over after the respray. It should just wash off.
If it doesnt your going to have to clay the car with a mild clay and plenty of clay lube.
HTH, Nige