If you use the CA Duster, just make sure you're supporting the weight of the brush and gliding the fibers over the car. You shouldn't be putting any pressure on the brush. My cousin used one on a dark green car for years without adding any visible scratches.

 

Some people use the duster as something more. Let's be clear, the duster should only be used on light "dust", not dirt. Also, I think I would think twice about even using it if it were on a brand new car but with used cars that already have some micro scratches, I don't think it's really going to matter.

BTW, I use the California Water Blade car squeegee to dry my car if I'm remote along with microfiber towel.

I thought this was crazy when it first came out then I saw a bunch of Ferrari enthusiast use it. I've been using it for over 5 years with very good results. But it has to be the California Water Blade as that has(had?) surgical silicone and "T" bar design. I've tried others and they do not compare.