What are you f**king up mate? It's not that difficult after some practice tbh, it's more about patience than anything else.
Clean off.
Sand down, thoroughly, don't be afraid to start off with metal files/very harsh paper.
Clean, big time, remove all grease and s**te.
Primer, three layers at least, thin-ish coats, don't let it get thick and run, 15 minutes inbetween, leave to dry for 24 hours.
If there are any imperfections, sand these back, and re-primer, leave for 24 hours...
Once you're happy with this, paint, at least three coats, same as the primer, not too thick, no runs, leave for 24 hours.
If you mess it up, just sand back lightly, one more coat over the top. Leave for 24 hours again.
Lacquer, this time, not 15 minutes inbetween coats, just until it's tacky. Two/three coats.