Let me cover some basics about shoe polish and shoe polishing in general:
There are 3 basic types of shoe polish:
Liquid – Not recommended for long term shoe care. If you have a bottle of this please throw it away.
Typically comes in a plastic bottle with a sponge tip applicator.
Cream – Base coat and brush shine.
Typically comes in a small, short, glass jar.
Paste – Final coats and spit shine.
Typically comes in a short, round, metal tin.
There are only 3 types of wax, all of which are used in shoe polish, either individually or in some combination:
Petroleum based wax – Paraffin
Plant based wax – Carnauba wax
Insect based wax – Beeswax
Shoe polish also contains oils for keeping the leather fiber of the shoe supple and to slow down the leather oxidation process. The most common are:
Lanolin – Produced by sheep skin oil glands.
Mink Oil – Extracted from fat cells of mink pelts.
Neatsfoot Oil – Extracted from the shin or foot (not hoof) of cattle.
Other oils such as tallow (animal fat in general) and Collagen (a group of proteins) are also used to some degree, however plant oils like Olive oil, Peanut oil, etc… are not used.
The oils listed above (not plant oils) are also what makes up most leather conditioners, to one degree or another.
Shoe leather usually comes from the tannery with around 17% oil content. It is important to try to keep the oil content around this ratio if possible. This is done by using leather conditioner periodically and keeping the shoes polished.
Shoe polish also contains solvents. The solvents are used to soften the wax and make it easier to apply. Shortly after the wax is applied the solvents evaporate. When a tin of shoe paste dries up and cracks it is because the solvents have evaporated, not because the oil has dried up. The most common solvents are:
Naphtha – Petroleum distillate
Turpentine – Pine Tree resin distillate
Stoddard Solution – Mineral Spirits
Shoe polish can also contain Gum Arabic as a viscosity stabilizer, and of course dyes for coloring.
The quality of a shoe polish is determined by which of each of these elements are used and in what ratios. Unfortunately, makers of shoe polish rarely publish the composition of their polish.
As for the difference in shoe cream and shoe paste (both are shoe polish): Shoe cream has a higher oil content and a lower wax content, and shoe paste is just the opposite with a lower oil content and a higher wax content. Because of this a spit shine is not possible with shoe cream. But, shoe cream does a better job of conditioning the shoe leather than shoe paste that is why some people use both to polish a shoe.
If you are not trying to put a spit shine on a shoe then shoe cream is best to use, as it will condition the shoe better and still produce a good brush shine.
If you are trying to spit shine a shoe, shoe cream is not needed as long as the shoe is well conditioned, the wax ratio in the shoe paste will allow for a hard wax shell to be created.
When thinking about actually producing a shine on a shoe it helps to think microscopically. The surface of the wax is what creates the shine. If you were to apply wax to a shoe (with whatever method –shoe dauber, cotton cloth, etc…) and then look at it with a microscope it would be very rough and inconsistent.
Running the bristles of a shoe brush over the wax repeatedly would smooth out the wax a great deal, leaving just microscopic valleys where the bristles had been drawn back and forth. To the naked eye the wax would be smooth enough to reflect enough light to make the shoes look shiny. This would be a brush shine.
To produce a spit shine the wax has to be much smoother. This is done by rubbing the wax with a smooth object with extremely little drag (this is where just a little water comes in handy) that contours to the surface of the shoe (cotton ball, or cotton wrapped finger). Multiple coats may also be necessary to fill in any imperfections in the surface.
Note that very little polish should be used to produce each coat, and that you are not actually adding coats, but rather blending coats because the wax being applied each time still contains some solvent.
Once the wax is smooth enough you will begin to feel a slighty oily tactile feedback as you polish, this is due to the oil that is inherent in the wax itself becoming the molecular barrier (along with a few molecules of water) between two very smooth wax covered surfaces (the shoe and the applicator). This is when the best spit shine will occur.