~ One man’s opinion / observations ~
Providing the brush you use has soft bristles (a horse hair brush is better) as opposed to nylon etc that will scratch the surface there is nothing magical about application.
The really important thing about leather care is the product used being suitable for the surface as not all leathers are the same. Most leather used in automobiles is coated with urethane so it requires a product that will permeate the coating to condition the leather underneath.
Cleaning- use a soft horse hair brush (Groit's Leather & Interior Brush) and/or a vacuum to remove any dust, apply a cleaning solution (Water /Woolite® or Dreft® 6:1 ratio or stronger) on to an applicator pad and apply to one area at a time (i.e. a seat back). To remove stubborn dirt or grime gently agitate the surface with a boar's hair cleaning brush (this will not harm the leather) then use a clean, damp Microfiber towel to rinse.
Maintenance cleaning- use a cleaning solution (Water /Woolite® or Dreft® 10:1 ratio) on to an applicator pad and apply to one area at a time
Stubborn stains- dependent upon the leathers condition or how dirty it is consider using a leather-cleaning product. (Leatherique's Prestine Clean, Groit's Leather Cleaner or Autoglym Leather Cleaner)
Notes:
1. With all cleaning products, always test a small, indiscrete area first to ensure it won't discolour or stain the surface, and ensure that the pH of the product is suitable for the material.
2. The harsh use of chemicals actually keeps dirt trapped in the fibres of the leather. If you abuse or neglect your leather, it won't survive
3. Do not use- Saddle soap (it's made to clean an entirely different type of leather), abrasive cleaners, furniture leather polish (they contain a wax), products that contain harsh solvent s or alcohol, as they will cause the stitching to fray and eventually break, petroleum distillate, bleach or ammonia based products.
Keeping leather clean is important, but conditioning is the key to preserving its useful life, flexibility, appearance and longevity.
Some recommended products
Urethane Coated Leather- use Zanio Leather in a Bottle Z10, Groit's Leather Care or lz einszett® Leather Care "Lederpflege"
PS: Knowing the type of leather would help to be more specific
with care recommendations, although 5:1 water/Woolite will clean just about all leathers
~Hope this helps~
Knowledge unshared is experience wasted
justadumbarchitect / so I question everything/ Jon