In my opinion the best way to prevent scratches/swirl marks is by being careful.
Use a clean bucket with good car wash and a microfibre or a soft wool mitt in straight lines from front to back.
I use a soft wool mitt, but am looking for a good microfibre one.
Keep a second bucket of clean water to rinse your mitt. Youll be suprised how dirty that bucket gets and how clean the soapy water stays.
Wash your wheels first with their own mitt.
Then wash the top horizontal surfaces (roof and bonnet), then the glass then the sides - top to bottom.
Do one section at a time and rinse after each.
Use a separate mitt for the very bottom of the doors/bumpers.
Use free running water for the final rinse (not a water jet or power hose ) since it will allow the water to sheet off better allowing quicker drying. If poss pack on a slight incline - this will also help with the sheeting.
And dont wash your car in the sun.
Dry with a 100% cotton towel (with NO polyester - as polyester scratches) or a natural or synthetic chamois with very little pressure. I use a synthetic one - as the feel of real wet chamois makes me squirm(??)
When applying waxes/polish/glaze etc. follow the directions on the bottle closely. Use a back n forth motion, not circular
Wash all applicators, buffing cloths, wash mitts and towels after each use. If anything falls on the ground, wash it before using it again.
I use a non bio liquid washing detergent. Dont use fabric softeners.
Cut off the towel labels, and the end stitching since even 100% cotton towels may use polyester thread - use a lighter to determine this, if it burns like a wick its cotton, if it melts with black smoke and has a black melted ball on the end, it is polyester.
Wash off bird crap immediately.
Hope this helps
H