Getting a smooth finish with enamel requires the correct combination of air pressure, paint viscosity and technique. You may want to make sure you are using slow dry reducer or try adding more reducer to your final coat. It's just a balancing act between getting orange peel at one extreme or runs at the other. The paint has to go down wet enough to "flow out" but not so wet that it runs.
My STRONG suggestion is to work all these things out on test parts before you go wading in with no experience. A finish product is no place for experimentation.
Enamel cures, it doesn't dry. If you are going to paint over it wait for it to cure completely, wet sand with like 400 and do your next coat. A fresh coat over an unsanded base will not adhere well because the new coat does not rewet the underlying paint. Applying another coat over partially cured enamel will not adhere well either because the initial coat is still out gassing.
One way to tell if the enamel is cured is to smell it. If you smell paint, it ain't cured. I would wait at least a month... in the summer. Impatience here will only bite you later.
Back in the day, a painter who could properly paint enamel was a valued commodity (not unlike the chef in a fine restaurant) in any auto body shop because if the paint was glossy with no runs the time saved was worth big money. If you screwed up an enamel job the consequences were a nightmare because you'd have to literally wash the paint off with reducer and do it again. Of course, you could try to convince the customer to bring it back in a month so you could sand out the run and repaint, but you can imagine how often that worked.
A properly applied enamel job is a thing of beauty, but a difficult learned skill.
