Clay Bar 

My favourite decontamination tool is still the clay bar. The light clay be Chemical Guys WA – Canning Vale for under $18 is an awesome clay that is very efficient in removing contaminants that is safe on all paint finishes. 
My advice is to use the clay lubricant with a clay bar. The lubricant allows the clay to glide over the surface to eliminate or reduce marring. (marring are ultra fine scratches usually less than a fee microns.)