I use Optimum No Rinse Wash and Shine (ONR) and Costco 36 microfiber towels. One bucket, 30 minutes. Nitrile gloves, Unheated garage, Northern Michigan winters.
Note, sometimes using automatic car washer on Model 3s has caused charge port to open and get damaged.
RTFM
Owners manual pp 135
Cleaning the Exterior
To prevent damage to the paint, immediately remove corrosive substances (bird droppings, tree resin, dead insects, tar spots, road salt, industrial fallout, etc.). Do not wait until Model 3 is due for a complete wash. If necessary, use denatured alcohol to remove tar spots and stubborn grease stains, then immediately wash the area with water and a mild, non- detergent soap to remove the alcohol.
Follow these steps when washing the exterior of Model 3:
1. Rinse Thoroughly
Before washing, flush grime and grit from the bodywork using a hose. Flush away accumulations of mud in areas where debris easily collects (such as wheel arches and panel seams). If salt has been used on the highways (such as during winter months), thoroughly rinse all traces of road salt from the underside of the vehicle.
2. Hand Wash
Hand wash Model 3 using a clean soft cloth and cold or lukewarm water containing a mild, high-quality car shampoo.
3. Rinse with Clean Water
After washing, rinse with clean water to
prevent soap from drying on the surfaces.
4. Dry Thoroughly and Clean Exterior Glass
After washing and rinsing, dry thoroughly with a chamois.
Clean windows and mirrors using an automotive glass cleaner. Do not scrape, or use any abrasive cleaning fluid on glass or mirrored surfaces.
Cautions for Exterior Cleaning
Caution: Do not use windshield treatment fluids. Doing so can interfere with wiper friction and cause a chattering sound.
Caution: Do not use hot water or detergents.
Caution: Do not wash in direct sunlight.
Caution: If using a pressure washer, maintain a distance of at least 12" (30 cm) between the nozzle and the surface of Model 3. Keep the nozzle moving and do not concentrate the water jet on any one area.
Caution: Do not aim water hoses directly at window, door or hood seals, or through wheel apertures onto brake components.
Caution: Avoid using tight-napped or rough cloths, such as washing mitts.
Caution: If washing in an automatic car wash, use Touchless car washes only. These car washes have no parts (brushes, etc.) that touch the surfaces of Model 3. Using any other type of car wash could cause damage that is not covered by the warranty.