Blushing is usually caused by high humidity. If you wait until a dry day and spray a light coat of thinner it will generally make the blush disappear. I use Certified Coatings or Randolph brand dope and both companies make a retarder for butyrate and nitrate dope. The various brands seem to be interchangable, but If you use a product not made for dope, there is the risk that it won't dry at all.