Not sure what it is I can tell you to help.
Yes, TSC paint is industrial enamel, and that is the lowest grade paint you can get.
If you going to use industrial enamel again, you can get a good result with it, but it depends on the weather conditions you spray it at, as far as how you should reduce it. A good rule of thumb is reduce it enough to get it to spray out well, but not a drop more. Do some test panels before you spray things that matter.
I usually reduce it with xylene, but other reducers can be used.
You can do a mist, or drop coat to even out the metalic, after you finish putting on the last coat, if necessary. This can include reducing the paint more, and misting it lightly from 2-3 times the distance further away. But, keep in mind doing this can also sometimes reduce the overall gloss when it dries.
Yes, the hardener will help it cure faster, and improve gloss. Even with the hardener, it takes weeks for industrial enamel to start to develop a good cure. Putting it in the sun for several days, can help drive the solvents out of it, which helps speed up the cure time.
Especially if your going to use the hardener, make sure you use a proper new charcoal filtered respirator. You can buy a disposable one for around $25, keep it sealed in the bag when your not wearing it. Once it smells like beer BEFORE you put it on, it has been used up, and your ready for a new one.
If you really want a good finish, I would use an automotive system on it, rather than industrial enamel. But, it will cost you considerably more money.