Here's a tip; I use the hardners in ALL my enamel paint. Testors little bottles, model spray paint (take it out of the can and use it in an air brush), everything. Does the same wonders for those paints that it does for the fancy car paints. Of course test a little first. Be my luck that it didn't work and ruined your $$$$$$ project and you would put a contact out on me. It has worked in all the paints I have tried it on.
Good advice though to use brand name stuff in the high buck auto paint, but do use it - it is great stuff.