Surprisingly good results can be achieved by following a method outlined below.

It should be noted that many people fall for the ‘three card trick’ by trying to wipe them off with a damp cloth. This makes the wall worse creating a huge, dirty smear that is nearly impossible to remove...even if its a single ‘dustie’.  

Follow this method:

1. Low pressure rinse the surface to remove the excess of grime....don’t try to clean the surface. A quick rinse is all that is needed 

2. To about 2 pints of water, add half a cup of  Feltpen Fadeout to make a detergent. 

3. Whilst the wall is wet apply the detergent mixture by using a window cleaners bucket and broom and agitate the wall in small sections as you go. Do not let the detergent dry on the wall.

4. Immediately pressure wash the wall which should remove many dusties. 

5. Any shadows of 'dusties' can be removed in the normal way with  Sensitive Surface Graffiti Remover where it is brushed on and immediately wiped off with a damp cloth. 

Excess agitation is usually not necessary.