This is what you can and cant do.

Enamel will go over anything, 2 pack medium solid, high solid, enamel it's self and acrylic.

acrylic will go over all 2 component products and it's self. It wont go over unhardened enamel.

2 pack in HS and MS will go over it's self and hardened enamel. It wont go over acrylic or unhardened enamel. The reason is acrylic and unhardened enamel never really fully cures and on a hot day will fingerprint. So painting a paint such as 2 pack over the top is like spraying over a jelly surface and as soon as it gets hot the jelly surface moves causing to 2 pack to crack, craze and sometimes solvent boil.

A lot better option then enamel in a can is to use 2 pack with a converter which is available from most automotive paint stores. I have it in common colours and clear which I use a bit for touching up small areas when I cant be stuffed making it up on the machine and putting it though a gun.

Cheers Mick.