Good thread and great answers, all I want to do is chime in with just a little tidbit of information.
For most waxes and paint sealants, (most not all), the idea is to apply the product as a thin coating working the product into the paint as much as possible. Under a microscope paint is not 1005 flat, it has little hills and valleys, pits and pores, and as it ages it has interstices, which means microscopic cracks and fissures. When you apply a coat of wax you want to try to push the wax, (or paint sealant), into all these sub-surface imperfections.
Next, let the product dry to a haze or until it swipes clear.
After it has dried, remove the excess softly using a premium quality microfiber polishing cloth.
After that...
quit touching it and let the protection ingredients you have deposited on the surface completely set-up, harden and bond to the paint.
Each time you give the paint another wipe you disrupt the coating you have just applied and push the protection ingredients around and 'yes' even remove them which is the opposite of what you're trying to do.
Even if the finish doesn't look 100% even, if you can wait, then do wait and let the coating fully set-up.
The 12 to 24 hour rule is just a guideline, it's a window-of-time to let pass so that all the protection ingredients have fully set-up.
The reason this window of time is vague is because you don't know at the microscopic surface level which areas are fully set-up and which areas are not, so you let a window-of-time go by before you either,
- Apply another coat
- Give the paint a final wipe
Just to note, it's not always possible to wait to give the paint a second coating. For example, when I do mobile detailing, if my customer lives a long ways from me then I'm probably not going to be back the next day, (12 hours later), so I wait about a 1/2 hour or so and then apply my second coat.
Two coats of wax or paint sealant insures,
- Uniform Coverage
- Uniform Appearance
So apply one coat, let it dry, wipe it off and if you do a good job in most cases that's enough. If you can
and want to, apply two coats and let your schedule in part determine how long you wait to apply this second coat.
None of us live in a perfect world so we have to let our schedules play a factor in how long we wait to apply a second, or even third coating of wax or paint sealant but the above stated reason is why you want to quit touching the paint after you wipe off any number of coats of wax or paint sealant.