The key word with the SG is "sparingly." The application should be barely visible, except from a sharp angle. It's kind of a "trust that it's on there" kind of thing. After 24 hours, you should add a second layer, and a third 24 hours after that (or wait up to a week between layers, but be sure to re-wash before applying). Three coats seems to be the limit as to how many will improve appearance (slightly each time), it is also a good number to ensure complete coverage. Longevity of the protection and look is gained with each additional coat.
You also need to work in very small areas (quarter hood, half door, etc.), if you are going to use the wipe on wipe off method. I wouldn't recommend the water spritz. Some seem to use it with success, but I believe it is recommended that SG be kept away from moisture for at least 24 hours in order to bond properly. I would instead recommed you look for some Sonus brand Acrylic Spritz. It is very useful both during the application process and as a quick detailer for bird bombs and light dust.