stedi Hobby Model Polishing Tools 3 PCS, Precision Glass Polishing Files #600-800 Grits, Anti-Slip Comfortable Grip for Gundam, Scale Military Model, 3D Resin Parts

I've seen others mention this but the main reason is that you want to use the files with the dots instead of the lines, like these here. I went through the same experience, got the ones you have and they scratch easily. The dot ones linked are much better and easier to use.