If your getting curtains your putting too much on. Old school coach painters would never attempt enamel in one coat. Their approach was to thin it to almost translucent and almost dust it on in layers with a flour paper down between. It’s a long winded process with huge amounts of drying time but that is how enamel rocks.
We have the advantage of scotchbright pads these days but they weren’t devoid of pumice dust on a damp rag.
I had the honour of working with an old boy who coach painted from being a kid. He’s long passed now but gave me a huge insight to the old ways. He taught me that because enamel is a hard finish to sand back between coats, the best way was to mix the primer with it in decreasing amounts. So pure primer first coat. Enamel with primer 50/50 on the next coat. 25/75 etc etc.
the slow colour change also helps with the subsequent passes.
Look on the bright side. He told me a story of one car company applying 16 coats to their vehicles.
