I was looking for the most common mistake that leads to swirls. There are too many pro detailers using a one bucket method and no grit guards without issues so my guess there is something else.
The most common causes of scratches to a paint film surface
•Improper methodology / tools used when washing paint surface. This is the most common cause of surface scratching / marring) and accounts for as much as 75% + of surface marring
•A large proportion of all paintwork scratches are caused by automated car washes. Minute particles of hard materials, such as road dust and sand, become lodged in the rotating brushes and etch scratches into the paint surface. These “hair-line” scratches are particularly noticeable in darker paint shades.
•Using an automated car wash or using an unsuitable applicator or brush to clean the vehicle or remove snow etc
•Placing or dragging an object across the boot lid
•Jewellery (rings, bracelets, etc) coming into contact with paint (i.e. rings abrading door handle recess)
•Using too much pressure with a car duster on a dusty / dirty surface
•Pulling a car-cover over a very dusty / dirty vehicle or dirt /grit on the inside of the cover
•Wiping a dry surface with a dry cloth
•Infrequent rinsing of brush or wash mitt when washing vehicle
•Using a dirty towel (dirt / grit trapped in fibres) or towels and / or applicators that contain polyester (plastic) threads
•Using a towel or cloth that is unsuitable for paint film surfaces
•Not thoroughly rinsing road grime before drying
•Using a car wash concentrate that doesn’t suspend grit / dirt before it gets rinsed away
•Improper use of a water-blade (i.e. not rinsing blade surface after each pass)
•Wiping a spot of dirt / dust with your hands to maintain a ‘pristine’ look
•Using an unnecessarily abrasive automotive detailer’s clay or insufficient lubrication
An extract from one of a series of 110 in-depth, unbiased “Detailing Technical Papers” © TOGWT ™ Ltd Copyright 2002-2009, all rights reserved.