IM not too sure if the reach is doable using the step.  
  I bought an extension telescoping handle brush to clean it.   
Then dry it using the 'Absorber' towel .
   
 ABSORBOR Towel :    you use and store the Absorber damp, inside its plastic tube.  It works GREAT on glass.  All I need to do is throw it onto the windshield then drag it across the glass.  It dries the clean glass in one swipe. 
 Its like magic . u can get it online or at Wally. Don't buy a knockoff store brand.  Get the larger Absorber, 27x17,  it reaches across half the windshield.   I use it to wipe down the shower too. Really makes life easy.