I have not attempted to do this, but if I were to try, I think I would spray the body with the primer of choice, then once dry, apply small amounts of liquid mask with a detail brush, or even a toothpick for tiny chipped paint areas. Then paint the body, and once the paint has cured, remove the small bits of liquid mask. It helps to make your liquid mask spots as thick as possible. In place of liquid mask, something like small bits of silly putty might work.
Another thought is the salt method, but I've never tried it and can't comment on a procedure. Perhaps someone who has tried this method will chime in with practical advice on how to do it, and if it would be suitable for this purpose.