dust on painted areas
One problem that was not mentioned is the area you are using, once carefully cleaned, try hanging some damp newspaper around your painting area, hang it up on strings like christmas cards, this will attract dust particles and cause them to stick to the paper not your paintwork.
Also try using Tac rags, both on your paint surface and the surrounding area.
Get them from car paint specialists, or Ebay, expensive from Halfords
Mark