HI Pipster
First you need to look at what caused the poor paint finish, If you were spraying in cool damp conditions that will cause a lot of your problems, also if the rattle cans were not shaken properly and were warm themselves.
Leveler does nothing for the gloss finnish it levels lumpy paint work, it does this by partially dissolving the paint and allowing it to find its own level so smoothing the surface.
Using any type of buffing / cutting compound, you must allow the paint to harden. Any time from 24 hours, onwards, it depends on type of paint and the temperature and humidity,
Is it possible that your poor finish is due to overspray and you have a 'sandpaper' finish? when spraying hang damp newspaper or towels / sheets around your work area, this will hold the dust in the air, stop it landing on your painted finish.
Hope this helps
Mark