More often than not, we over apply most products making them difficult to work with and wasting a lot of good product in the meantime.
When applying this or any other product using a dual action polisher you may initially see a bit of ghosting as you move the machine and pad back and forth. As you continue even this becomes very hard to see as it becomes thinner and thinner.
When you think about the actual film thickness of the protective layer it's mind-boggling. The way I understand this is we're talking about 1/50th of a nanometer, or 20 Ångström typically.
To put it in perspective, there are 25.4 micron in 0.001 inch...
1 nanometer = 10 Ångström
1 micron = 1000 nanometers
Personally, I feel you have adequate coverage...