I have been using the same procedure for years using the Chemical Guys blade. It is obvious that if you don't clean your car properly in the first place by using snow foam and letting it dwell for a time then blast off the water a microscopic bit of grit could cause damage if a dry blade went across it.
All I can say is that I've been using the same method for many years on two black cars (one of which won an award for shiniest car) and the guy who does my detailing has never once said there are scratches on your car caused by the use of a blade.
All I can say is that I've been using the same method for many years on two black cars (one of which won an award for shiniest car) and the guy who does my detailing has never once said there are scratches on your car caused by the use of a blade.