the sanding of the base is critical and application of the paint itself, Long smooth strokes with a very BIG compressor that has atleast a 3 stage filtration process is mandatory. Not the little rackety item most Pakistani painters have.
It ensures no moisture, no pulsing and even spraying.
Sanding should be helped with a pepper coat of black or gray - the peppering is done so see whether a surface is raised or dimpled. Rubbing of the pepper coat will show a higher surface, which needs hammering correction. You cannot eliminate orange peel 100% unless you dip the car in paint. But most shops make sure to get the least possible (finest) of it then polish it out.