Car looks great!
CQUK can certainly be quite finicky in higher heat and humidity. It is essentially wipe on/wipe off, and larger panels (hood, roof, etc) should be broken into smaller sections. Depending on the temp, I usually will not coat a panel larger than 1 door at a time and often break doors into 2 sections.
CQuartz Classic is considerably easier to use in higher temp. My personal favorite silica based coating to use in most temps would be 22ple products. For non-silica coatings, Optimum Gloss Coat has to be the easiest out there.
-Zach