Polishing shoes is more of an art than a science, because there are so many methods to accomplish the same thing. There is no “one” best way to polish shoes, but there are some basics that remain consistent.
The component in shoe polish that makes a shoe actually shine is the wax. The only exception to this would be liquid shoe polish, which should never be used.
Other ingredients in shoe polish serve different purposes such as oil to condition the leather, dye to help cover scuff marks, and solvents to help soften the wax during application. But it is the wax that produces the shine.
So the question really is “how does wax produce a shine on a shoe?”
When the polish is applied to the shoe the oil is absorbed into the leather, and the solvents evaporate (mostly during the application process). The shine comes from flattening out the wax over a relatively smooth surface (the shoe sides/quarters, toe, heel and vamp).
As you apply polish to a shoe you are smearing the wax across the leather surface with either a cotton cloth applicator or dauber brush (I use a folded cotton round). This is the point where thinking small (microscope small) comes in handy.
While the surface of the shoe leather is relatively smooth it is not perfectly smooth. Even though leather is given a finished surface at the tannery it is still porous to some degree, and has microscopic hills and valleys in the surface of the leather.
As the wax is applied to the shoe, the wax also has hills and valleys which is why a shoe brush is used to smooth it out.
Since the vamp flexes more than any other part of the shoe, it benefits less from the polishing/smoothing aspect of the wax than other parts of the shoe that are rigid, and therefore less wax is necessary on the vamp.
This is why I always make a point of distinguishing between cream polish and paste polish, because cream polish has a higher ratio of oil to wax than paste polish which has a higher ratio of wax to oil. Using cream polish on the vamp adds more oil to the leather where it is most needed (the flexible vamp), and less wax than paste polish.
Due to the molecular structure of wax, once on the shoe it doesn’t come off easily (unless it was applied way too thick). Trying to rub all the wax off your shoe with a cloth, and no solvent, is quite a task – even with just a light coat of wax. Brushing a shoe will remove a very, very small amount of wax, but enough that you would want to have different shoe brushes for your tan loafers and your black cap toes.
The main purpose of brushing a shoe with a shoe brush is to spread out and smooth the existing wax on the shoe. This will inherently cause a shine. The degree of shine is determined only by a couple of factors: 1) The remaining wax to oil ration in the polish (you can’t spit shine a shoe with cream polish, at least I can’t) and 2) the smoothness of the wax surface. The smoother the surface the wax is applied to the easier it is to create a smooth wax surface.
Since once you put wax on a shoe it remains there for quite some time, unless it is purposely stripped off, each time you brush a shoe you are again spreading and smoothing the existing wax, and will produce a shine of some degree, without adding any new polish to the shoe. If at some point you are unable to produce a brush shine it is most likely due to the wax getting too dirty, and it should be stripped and replaced (and the shoe conditioned with oils after the wax is stripped).
When you start with a less smooth surface, or want a brighter shine (like a spit shine), it takes more coats of wax to create a smoother and smoother surface. When you get to the point of a spit shine the surface of the wax is like a very thin hard candy coating. If the surface under the thin hard candy coating of wax flexes (as the vamp of a shoe does) that wax will fracture and lay in the creases of the shoe.
A light coat (or two) of cream polish brushed thoroughly into the vamp is all you really need for that area of the shoe. Anything more will cause the wax to fracture and the creases in the vamp will begin to look like they are starting to crack. Wiping of the excess wax with a damp cloth and brushing the shoe when you see this will help.
If you are not interested in a spit shine then this is about all of the polish you need to add to the entire shoe until the next time you clean and condition your shoes. In-between cleanings, just wipe off the dust and brush back to a shine with the existing polish on the shoe.
The more rigid areas of the shoe, like the back of the shoe and the toe, can support more coats of wax, which allow you to create a spit shine if desired.
A spit shine should not consist of more than six (6) coats of polish: A base of two coats colored cream polish, two coats of colored paste polish, and if desired, two coats of clear/neutral paste polish.
As each coat is added it creates a smoother base for the next coat. The last two coats of clear is to give the shine some depth. If you cannot obtain a spit shine with this number of coats there can only be one of two reasons: The quality of the shoe leather is not sufficient to be spit shined, or you need work on your technique (It is usually the second reason for the less experienced).
Why only six (6) coats? because as you add coats of wax you introduce a greater and greater instability within the medium. For example: take a stick of unwrapped butter, at refrigerator temperature, and slice in lengthwise six times. Then lay the slices on top of each other and secure the bottom piece so that it cannot move. Begin pushing forward and down on the top slice of butter. Even though the slices stick to each other to some degree it is not a solid structure. As you add more and more slices of butter the structure becomes less and less stable.
This is not a perfect example of what is happening, but it is similar. This is also why you want to apply less pressure when finishing the final coat of a spit shine.
A trick you can use to determine if a coat of polish has been sufficiently spread and smoothed out is to run your finger across the shoe slowly and gently, if feel anything more than the slightest drag on your finger then the wax has not been sufficiently spread and smoothed out, or you used too much polish on that coat.