[Designer]

Are you using standard (flat) cellulose paint or acrylic?

If your using cellulose, then just keep doing what you've done to build up the paint layers till you've got loads of layers on, then wetsand with progressively finer wet-and-dry paper, when you've got the surface imperfections out of the paintwork then use some good quality cutting compound like Carplan T-Cut (work that in small areas around 6" at a time). It's hard work but you should get a mirror finish back.

Hope this helps