Orange peel is primarily caused by too much air pressure, or being too close to the surface you are painting. The viscosity of the paint, the temperature, the humidity, the type of thinner and/or "dryer", and other environmental conditions, can all contribute to the problem.
I find that the best performance can be obtained from the paints if you use the same brand of thinner as the paint, eg Testors enamel and Testors recommended enamel thinner .
You can repair or correct the "orange peel" by sanding the surface smooth and recoating it. Because sanding can ruin "detail", and more paint can cover up detail, consider using Poly-S Paint and Decal Remover and start over.
It is also important to use FRESH paint and thinner that has been thouroughly mixed and filtered when it is poured into the paint cup or bottle for spraying. Just as important is having a PERFECTLY clean airbrush EVERY time you use it. Compressed air should be run through a filter/dryer. Lastly, never ever pour paint mixed with thinner back into the paint bottle.
Most of the work for a paint job is in the preparation.
Find a system of tools and products that works well for you.
If you ever get a PERFECT paint job, it is time to quit. Otherwise, lets keep striving for that perfect paint job. Cheers, rangerj