I think a lot of us "amateurs" do not realize the effects on how it all turns our is the temperature. Reduces, activators related to temp., and humidity.
I have always been successful with a metallic simply because I was so extremely aware of how it had to go down, especially that last coat.
my 2nd paint job was metalic, metalflake, and pearl
turned out great
I was a trash man and had 3 body shops on my route,
asked advice, one guy that turned out amazing paint said one thing,
mix the tack coat v thin for metallic/flake and let dry to almost dry,
second quick to help the paint stick,
put the paint down, ignoring shine, only even color across every panel, go slow
finish with the same thin mix you started with to shine it back up
thin coats, allow to cure well between coats
use high humidity reducer
paint lasted 25 years and 300k miles w/ touch ups
totally a "pay attention/patience game"
and when to start removing tape is an art, too
ruin a great green paint job pulling it too soon
esp high humidity, you think it's dry, and remove paint on the a pillar right off the bat
not a fun thing