Lonnie,
I am a novice amateur. Read other people's responses with greater confidence in their knowledge. I know what I did on my Suburban, and, I would change nothing.
> Is "Polyurethane Acrylic Enamel" the same as "Acrylic Enamel?"
2-part 2K urethane is different is different from Acrylic Enamel.
I do not know what Polyurethane Acrylic Enamel is - what would be a brand name?
> Do some/all enamels use a hardener?
2K urethanes do not need a hardener.
I have used a hardener with PPG Delstar Acrylic Enamel with excellent results.
> What's the results difference between enamel paint and 2K urethane paint?
The urethane is considered to be higher quality: longer wearing and able to highly buffed.
> After a couple of weeks curing, is one "tougher" than the other?
The urethane is considered to be "tougher".
Color sand (buff/polish) the urethane with 24/48 hrs - it gets real hard.
> Are they both about equally easy/difficult to shoot?
In my opinion, yes.
The urethane is usually more expensive than the acrylic enamel.
> Is one easier to flatten to a semi gloss than the other? How?
In my opinion, equal.
> How do each of the paints stand up to gasoline dribbles from a fill-up?
I have not had problems with the hardened PPG Delstar and PPG DCC.
