This gets confusing in terminology.
I just found out the Sherwin Williams has what I was told is a "single stage" urethane line of paint.
Both should be used with "hardeners" though.
And it's a "small" amount for each.
Different reducers and hardeners for each line of paint.
It's not like I was expecting with a urethane.
A "polyurethane" paint that I've used takes a lot more "hardener".
That's what I would think is a true "two part" paint.
Best I can figure out from the internet is that there is acrylic enamel and there is acrylic urethane.