The one I linked is applied to the vehicle while its still wet. Wash first and lightly spray a panel then rinse. I will do half of my Tacoma at a time, rewetting when necessary. As for the undercarriage, haven't tried it but I can tell you this, I accidentally spilled some on my garage concrete. I now have a slick ceramic spot there. Its been a year and I haven't "walked" on it enough to wear it off yet.
This whole ceramic thing started when I read something about it and posted a question somewhere. Almost all of the negative comments came from people who thought it made their paint indestructible. I can say it helps with the light bush marks I get from the various bushes I tend to scrape against. The ceramic soaks into the pores of the paint and strengthens it with a light coat over the top.
I started out with a tiny bottle of the ceramic concentrate. This stuff requires you to wash, claybar, polish, wash with a special soap to remove any wax, wash with a special cleaner then apply the ceramic. The process takes two days and the coating will last for two years. If you don't clean it properly, you will trap dirt or whatever under the ceramic.
The detail guys charge over a grand for this. I spent about $200 for everything and did it over a weekend. I can say, it did hold up well. water repelled off it like it was just waxed and lasted a bit over a year.
I was thinking about doing it again and was talking about it in one of my classes and it turned out one of my students owned a small detail business. He recommended the spray I linked to be used to keep adding layers to what I already had. He said he stopped doing the concentrate and had great results with just the spray on a clean car. About six months later, I end up with another detail guy in my class who agreed with what I had been told by the first guy and added a ceramic washing solution. This if used a couple times a week will slowly build the ceramic up and (or) maintain what you already have.
Now I use the carwash solution every two weeks and the spray bottle a couple times a year. As for the undercarriage, I never though about coating it. What I'm going to do now Is use the car wash solution in my foam gun and work up layers especially my fender wells. I will say this, brake dust cleans off easily, I don't see anything negative using it underneath.
As I said earlier, I don't use wax anymore. All my research has led me to this conclusion. Very few detail guys use wax anymore, with an exception of the old school guys. The car show people are beginning to go this way. The real expensive concentrate I used in the beginning shines like high end wax and is the favorite for the show guys I've met.
Here's what I use on everything
Wetcoat. Spray on a few times a year
Car wash solution. A gallon lasts me over a year. Only use a small amount, its concentrated.
UV spray for rubber/plastic
