For any coating, you have to prep the paint perfectly. Coatings can fill up very minor imperfections, but they aren't designed to do that. They will do nothing with deeper swirls, so when you lock them in with a coating, they are set.
Application is different too. Some coatings are sprayed on (most wasteful), some can be wiped on/off easily. Most of them has an absolutely grabby, bare paint feel yet they shed water like hot iron. The Optimum is a very friendly product as it can go on top of every surface & material and is slick. It has an excellent appearance too. Some coatings are designed for painted surfaces, but nono on plastics, glass, etc.
For the wipe-on types, a flat, lint free applicator is great. Better quality cosmetic makeup pads, flat, fine MF pads are excellent.
Layerability is a funny thing because as you try to apply a new coat over an existing one, the new one beads up immediately when sprayed on, and sometimes under the MF app. Yes, it can be done, but the application must be very focused to avoid a patchy, uneven result.
Don't wash the car for at least 48 hours (preferably 1-2 weeks).