Acrylic enamel stays soft a long time, some say forever,
even when using a hardener.
It's at the bottom of the line for durability.
Urethane is at the top for durability, it sets up rock hard in just a day
or two and is really hard to scratch off.
It's one of the toughest finishes available.
You can clear coat it just like a basecoat too.
I sometimes use it in place of a basecoat.