Hi - If you want to remove the paint entirely, try using an ammonia based window cleaner. Takes acryllic paint right off. I learned that trick by accident.
As for your problem with the cracking, I'm assuming the paint is not old. It may what you are thinning the paint with if airbrushing. Rubbing alcohol or some distilled water would work best. I have heard of acryllics cracking before, but have never had the problem myself using Gunze or Tamiya paints. Good luck...