Been using ONR for years and have never experienced what you are describing. When really covered with salt I've always pre-soaked with standard mix ONR in a small pump sprayer so by the time I get to that area the salt cake has softened. I've also always used these long nap MF mitts http://neatitems.com/Deep-Pile-Microfiber-Mitts.html I carefully remove the threads that create the finger pockets so there is just one larger pocket in the mitt -- I insert a grout spounge into the mitt--offers better control for light pressure and allows allot of solution to be used for really dirty areas.
