The key for me in understanding how to spit shine, after a LOT of trial and error, was to actually figure out HOW spit shining works.
Don't even bother with inferior polishes. You want Kiwi parade gloss, or Lincoln, which is THE polish used by the armed forces.
With new boots, an old trick is to apply Barbasol to the leather, and then brush it off, to make the leather as clean as possible. This gives you a good starting point to work from. You're trying to get the surface as clean as possible so that subsequent steps will have a solid foundation to work with. With a uniform flat surface, the upper layers won't be disrupted by naps, uneven patches, or whatnot. The prep work is important.
When you apply the polish and water, you'll be doing so with fabric wrapped around your forefinger and index finger. Put the cloth over the fingers, pull it taut, then wrap from around back, over the palm, and then clamp the thumb down to hold it there. That way you get a good surface, but also feedback, and control.
With a perfectly clean, fluffy nap leather surface, take a T-shirt or similar material held in the manner described above and work a layer of polish into the leather. Small circles, small areas at a time. Move to a different section as soon as you feel the slightest drag, which is why you are using your finger tips. You want a thin layer, but a good layer.
You've overdone it if it takes a long time to haze over and dry. You want it to happen fairly quickly, but still get a nice layer on it. You're trying to "fill in" the gaps and level out the surface of the leather to as flat and uniform a surface as you can.
While that's happening, soak a diaper or T-shirt in cold water, and have a tin of cold water or cold water in a spray bottle nearby. With a wet cloth (not dripping, but thoroughly damp) you go back and again make circles, polishing the leather. Do not use a brush, you don't want to introduce swirls. This process lubricates the polish and evens it out. You're trying to get as even a surface as possible.
Let that dry.
Repeat the application of polish / application/smoothing with water at least six times. Each time, go a little bit lighter in your application of polish, and a little bit lighter in the polishing. What you're doing is adding layers of depth. When cars had lacquer paint and paint jobs were incredibly gorgeous, cars were painted multiple times. Each successive coat was sandpapered with slightly finer grit - the final layer was polished with a cloth similar to peach skin. As a result, the eye saw the paint as mile deep and insanely glossy, and that's what you're doing with the shoe polish, here.
Here's the magic part. Ensure that your boots are TOTALLY dry. You don't want beads of moisture evaporating here. Take your time and wait for it to dry.
You will need a heat source for this. Some guys use an open flame, others a hair dryer. You get more control with the hair dryer, but it takes longer. Heat the polished boot until it just goes REALLY wet looking. That's the layers melting together and flattening out. Keep the heat on too long and it won't be flat, it will run. Do NOT get horridly disappointed when the surface hazes up after. IS. NO. PROBLEM. If you see a "cottage cheese" or mottled effect in the polish, keep adding more layers as above until you don't.
The last two to three layers, you barely graze the surface of the polish with your cloth, and you barely touch the boot with the polish, and you wet the snot out of the cloth when you polish - with almost NO pressure. You don't want to see the polish come off on your wet cloth: but what this will do is really polish those final top layers, and you WILL get a near-mirror finish. By skimming the surface you're trying to get the wax with little pigment. This is the near-wax only layers, and now you're just polishing up nothing more than carnuba wax.
Parade gloss caliber polish has higher concentrations of carnuba wax. It is these waxes, when pulled gently from the polish tin and buffed with near-zero pressure at high speed with the softest of cloths that gives it the bling. This is what goes from nice looking shoes to oh my God, I didn't know that was possible shoes.
After doing this, you can add a small engineering trick.
Do what I did and realize that the magic here is the carnuba wax. In various car care stores such as Pep Boys you can buy actual Honest To God Carnuba Wax, no fillers or polymers. Guess what I use for MY top two coats. READ THE LABEL to make sure it's carnuba wax. Don't screw it up at the last minute by introducing God knows what else. And that shines it all to an even more high-power high-candlepower gloss. You will understand finally how someone using highly polished black stone could use it as a mirror back in the olden days.
No need to use automatic buffers, and don't use brushes. Everl Brushes are to CLEAN shoes. You'll introduce scratches and imperfections that will mar the base. Just sacrifice some T-shirts and some nice microfibers that won't pill off and introduce fibers into your shine. Some use wet cotton wool for the top coat layers. Experiment and see what works for you, now you know the principle and the HOW it works.
To maintain your shine, spit up the last couple of layers with a gentle application, but with a topcoat of carnuba wax you should be able to simply dust gently with a damp cloth.
I never believed the adage "you could see your face in them." But by God, there it was, my ugly gurning mug grinning like a Cheshire cat at the frightening level of shine coming off my boots.