These brushes need to be "seasoned" before using them for real. The instructions recommend leaving them on a newspaper for a few days to draw out the excess wax. I do this, then use the brush on a dusty (not dirty like when it's been rained on or splashed) car just prior to being washed since it will leave streaks until it has released all the excess wax.
It will take a number of uses before it stops leaving streaks but after that, you can use it to remove the dust in between washes. I've been using these for decades with no ill effects. Ever been to a car show or watch auto auctions? Brushes are in use all the time so concern about them causing damage is unfounded.